On linuxcoin I experimented with phoenix+phatk but found that my CPU utilization went up sharply - from say 3% per miner to 20% or more.  I am heat-constrained, operating my caseless rigs in the crawl space under my Austin, Texas house without air-conditioning or extra fans, so poclbm appeared more watt-efficient, and also I had some stability issues, e.g. crashes when overclocking my Radeon HD 5770 GPUs to 960 MHz with phoenix.  In contrast, poclbm handles my overclocking OK.

I use linuxcoin and the kernel I edited was named BitcoinMiner.cl, located in /opt/miners/poclbm.

This simple change took each of my six 5770 GPUs, overclocked to 960 MHz, from 204 MH/sec to 212 MH/sec, a 4% increase!

I also believe that a more accurate model would be to apply the difficulty increase over an average duration - not daily.  The log charts at http://bitcoin.sipa.be/speed-ever.png are especially helpful in visualizing the steady, yet step-wise, increases.

Leaving aside speculation on when ASIC technology supersedes today's GPU technology, I assume that the difficulty will level off when a substantial number of miners quit due to high power and air conditioning charges due to their mining rigs. 

Worldwide, there is a large disparity in what miners pay for power.  For example, in Austin, Texas, USA, I pay about .13 USD per KWh.  My rigs are located in the crawl space under my house and operate without air conditioning.  They draw a total of 850 watts from the power socket.  That costs me about 2.63 USD daily.  I suppose that sometime in the next few months I'll be mining coins paying about 4 USD per day, and that difficulty will level off until the technology changes or BTC prices dramatically increase.

I stopped reading Slashdot about the time that I mined those two blocks of bitcoins back on July 12, 2010.  The main problem with Slashdot was that its primary moderator biased the chosen articles to what in retrospect seems to be a fairly narrow scope, e.g. anti-Microsoft, pro-open source, scruffy and so forth.

Each day I now rapidly scan the 60 most popular headlines on Hacker News http://news.ycombinator.com/news, and then also rapidly scan the 500-600 headlines posted on the New section overnight.  Hacker News is operated by the famous Y Combinator, i.e. Paul Graham, startup incubator, and anyone can post a headline there that roughly fits the interests of people who might form or otherwise participate in a startup company - namely the same sorts of people who love bitcoins.

Needless to say, there is some mention of bitcoins nearly every day, and my attention was drawn back to bitcoin mining after a 10 month hiatus by the continuing stream of Bitcoin articles on Hacker News.

Give it a try.  Its a sort of firehose, and most articles will be in some narrow tech area not of interest - but you probably will not miss out on the next big thing.  By the way that next big thing might very well be a new wave of startups involving the growing bitcoin economy.

I'm writing a set of Java clients for popular exchanges and for the last two days I've been debugging communications with the TradeHill API.  The error message has been ....

    Forbidden 403
   CSRF verification failed. Request aborted.

TradeHill says that they will look into their django server configuration regarding a possible fix that I found on the internet.

CSRF is an acronym for Cross Site Request Fraud, and what the original poster wants is for bitcoin financial web sites to enforce security so that someone else cannot hijack your session with the web site.  CSRF is a protocol in which the server sends to you a certain random token and which your client, e.g. web browser returns to prove that you are the same entity that originally started the session.

For example, TradeHill sends to me the following HTTP header when I perform an HTTP against their API URL at https://api-test.tradehill.com/APIv1/USD/GetBalance ..

Set-Cookie:  csrftoken=35d13f0f2708ee17b0834719b902ad65; Max-Age=31449600; Path=/  <== GENERATED BY TRADEHILL, UNIQUE FOR EACH SESSION

My subsequent API request must specify that token when performing an HTTP POST, e.g. ...

X-CSRFToken: 35d13f0f2708ee17b0834719b902ad65  <== PROVES THAT I ORIGINATED THE SESSION

I have 6 Radeon HD 5770 on three motherboards that I got from Newegg a few weeks ago given the limited choices.  Four are Sapphire cards that run 10 degrees C cooler than the alternatives.   One of the Sapphire HD 5770's crashes when overclocked so I leave it alone.

The three rigs yield say 1145 MH/sec and the shared UPS draws 850 watts.   I keep the rigs in the crawl space under my Austin home where the ambient temperature is 30 degrees C - with no air conditioning.

I am very satisfied with these cards for mining.

From Slashdot ...

http://news.slashdot.org/story/10/07/11/1747245/Bitcoin-Releases-Version-03

July 11, 2010.  The following day I generated 2 blocks on my just-configured quad-core CPU miner.  Then I ran the miner for the next several weeks before shutting it down.  There was a huge spike in difficulty and there were no pools back then to keep me going.

BTCGuild ...

Rewards Summary
You generated 1.1559097 BTC in the last 24 hours.

Back on July 12, 2010, I generated two blocks that day on my quad-core CPU rig - before the subsequent difficulty increase made me turn off the CPU miner.

Take a look at this cool new bitcoin mining calculator that incorporates projected difficulty increases....

http://striketeam.ath.cx/btccalc/btccalc.php

The first of many bitcoin billionaires will not be wealthy because of the number of bitcoins in their wallets.

Its clear to me that these billionaires will have created bitcoin businesses from scratch, or will have adapted existing businesses to bitcoins.

Mt Gox might have annualized fee revenues at the June rate of 24 000 000 USD.  Those revenues may value Mt Gox at say 100 million USD.  One can easily imagine Mt Gox expanding to 10 times their current transaction volumes and making their owners in effect billionaires.

Furthermore, suppose Amazon wholeheartedly adopts bitcoins to save on transaction fees, to the point where some time in the future, the majority of Amazon purchases are made with bitcoins.  Then Jeff Bezos would become a bitcoin billionaire, as he is already a dollar billionaire.

Check out this great new mining calculator ...

Using your figures ...

Month   BTC     USD     Difficulty
1       8.61    146.37  2674335.14667
2       2.82    47.94   8153044.98651
3       0.93    15.81   24855576.772
4       0.3     5.1     75775332.7365
5       0.1     1.7     231010573.764
6       0.03    0.51    704264610.441
7       0.01    0.17    2147038698
8       0       0       6545515850.71
9       0       0       19954823260.4
10      0       0       60834773062.1
11      0       0       185462410026
12      0       0       565405339767
 
Total   12.82   217.94

I don't believe that bitcoin values will ever stabilize like paper currencies. 

Central banks can control the amount of currency in circulation, in part to achieve short-term stable values. In contrast the ultimate number of bitcoins will be fixed.  Each person and business entity requires a certain amount of currency to conduct transactions.  I believe that this demanded amount of bitcoins will vary according to overall business conditions - growing during economic expansion and pausing/shrinking during economic contraction.

Informed speculators will be motivated to purchase and sell bitcoins in advance of expected economic expansion and contraction.  Thus I think that bitcoin prices will be similar to those experienced by commodities - and continue fluctuate as they do now.

Because people and businesses seek stable currency values, I think that one or more to-be-created bitcoin futures markets will offer currency instruments derived from bitcoins that promise a certain, more stable value, e.g. US dollars, for a certain duration.  Prices could then be quoted in say December Bitcoins, with the buyer and seller knowing that this value will be say exactly 30 USD from now until December.

And so it begins ...

Recent miners hurrying to sell their rigs before mining becomes unprofitable given exponentially increasing difficulty and perhaps less exponentially increasing bitcoin value.

What goes first?  The 6990 space heaters?

Can you make linuxcoin a choice?  It deserves a separate mention.

That's what I use!

What are the ordinary transaction fees to buy or sell bitcoins?  [Will you beat Mt Gox and TradeHill?] 

Will you consider a tiered fee structure for active traders.?

Are there fees for withdrawing or adding funds to my account?

I looked in the FAQ but could not see this info.

Like others I desire a trading API - hopefully subsuming the Mt Gox precedent.

The x86 and ARM CPU ALU are way too powerful, and way too few in number, to be efficient bitcoin miners.  Their architecture is designed to execute general purpose threads and thus are not sufficiently optimized when compared to the Stream Processing Units on the AMD Radeon graphics cards.

For example the HD 5770 cards that I use each have *800* Stream Processing Units overclocked to 960 MHz.  Each Stream Processing Unit takes a tiny fraction of the chip die space occupied by an x86 CPU ALU.  So for each lithography generation, there will be many more Stream Processing Units per chip than x86 ALUs - like 100 times more!

Its likely that in the future that chips will be manufactured expressly for bitcoin mining - see the ASIC discussions on this forum.  These are supposed to easily surpass existing AMD graphics card performance and power-efficiency.

Although the poster expresses a preference for raw power, anyone else considering a new bitcoin mining rig should optimise three separate features...

1. maximum MH/sec per GPU card - fewer GPU cards mean fewer motherboards, CPUs, and power supplies, software configuration, and monitoring effort.

2. minimum purchase expense per card - with mining difficulty exponentially increasing due to exponential growth of total network hashrate, its possible that certain expensive mining rigs will not payback their purchase price after subtracting gains from selling off the used components later.

3. minimum power consumption per card - this ongoing cost determines the point at which bitcoin mining ultimately becomes unprofitable on a cash flow basis.  Lower power consumption per card makes it easier to cool the card and also to overclock it.

The Radeon HD 6990 is optimal only for criteria #1 above.  The owner of the famous 48 GH/sec mining rig featured on YouTube says that he is "upgrading" his vast number of 6990 cards with 5830s as he can obtain them.  Why?  Because of criteria #3 above.

I chose to construct my 1200 MH/sec rig using three case-less motherboards with two overclocked HD 5770 GPU cards each.  The HD 5770 cards were the most optimal for me using these criteria considering the limited choices at Newegg in the USA at the time of purchase.  The power drawn by the shared UPS is 850 watts.

The problem of lost passwords for default-encrypted wallet.dat files is already solved by existing online password storage services...

For example: http://www.passpack.com/en/home/

One can easily image an entrepreneur on this forum offering such a service tailored for, and marketed to, bitcoin clients.

Even though the best video cards are not freely available in the US, they can be obtained in other parts of the world. 

It's likely that the vast majority of previously sold Radeon 5XXX and 6XXX cards are *not* currently used for bitcoin mining. Therefore, I think a larger source of new miners are existing Radeon 5XXX and 6XXX gaming enthusiasts who can easily install mining software on their otherwise idle game computers. 

As a landlord, its been my experience that the poor choose cash for transactions over more expensive alternatives, e.g. checks, money orders, and credit cards.  The poor are compelled to use the cheapest means of conducting transactions.  The alternatives have fees that the poor cannot afford.

Bitcoins are cheaper to circulate than paper money.  One needs only some form of internet connection and they will become ubiquitous with smartphones.

Bitcoin speculation favors the rich however, in that the rich have the speculative funds to begin hoarding bitcoins for potential appreciation.  One could expect the poor on the other hand to spend every bitcoin that they possess and not hoard at all.