I think this understates the actual costs. Assuming you want to run an SP20 at it's full speed, you will need a high quality 1300 Watt (or so) power supply. Just based on your previous experience, I'll bet you don't have a dozen 1300W power supplies just languishing in your closet waiting to be used. I would also mention that regardless of the actual costs, a dozen SP20's will be really loud based on other folks experience, particularly if you try and extract the maximum hashrate. What I have read is that the SP20 is really more like a 1500GH miner with 1700GH being a fairly reliable "overclock".  Spondoolies fully supports the 1700GH rate, it's just that it's power efficiency is poor at that rate, and expect at it's loudest (because the fan is at it's maximum).

There are lots of excellent threads here on the SP20 that can keep you informed. I think it's an excellent miner, possibly even for home use. Just make sure your eyes are open.

My recollection is that with the setting of timed "actions", the time specified must be in UTC. Of course if you live in Greenwich England, this won't matter. This is kinda a surprise, but not so much when consider that Linux is inside there.

You calculations are largely correct, even for a fictional miner. While you might get a return that matches the cost of your hardware, it won't be a lot of money. The real miners (e.g. Spondoolies, Bitmain, Aavalon), aren't really in better shape for a return on your money. They do exist though, and you will almost certainly receive something real for your money, and in a timeframe that makes sense (i.e. not months).

I also think xstr8guy is being too generous. Even for a well respected companies, pre-orders carry some significant risk of massive delay, or non-completiong or delivery.

I'll add my two cents with a question. How bad will it impact you financially if you lose your entire $5K "investment"? Once you have than answer, you can decide how much to put into buying, and into mining. I would discourage you from just finding $5k of hardware to buy and hoping for the best. You will NOT get rich doing that. I didn't actually buy any Bitcoin, until long after I had been mining. That in my opinion was a mistake.

One other item I have discovered, is that your best path to making some money by mining, is to be prepared to sell some or most of the mining gear you purchased within 6 months. There comes a point during the life cycle of a specific mining hardware that it has produced something for you, and it's residual a value.  That peak "used" value is usually long before 6 months.

While interesting, this can't be a surprise to anyone. Didn't they just recently get kicked out of their Data Center and have to suspend operations? The Chapter 7 filing is more confirmation of their status than anything else.

I have run an RPi with both U1 and U2 with bfgminer. I don't recall the bfgminer level. I always had the U1 and U2 on a solid powered hub (e.g. a 7 port Dlink with plenty of power). What I always did was after I booted the Rpi, but before I tried to run bfgminer, I would look for and count the /dev/ttyUSB* entries. There should be one for each U1/U2. That tells you if the Pi
has recognized them. I also recall having to build bfgminer with some specific argument to make sure it had the right driver, and recognition software included.

This may all be moot if you are happy with cgminer.

Regardless of the mining software, you will want the U1/U2 on a powered hub. 

I guess it's no surprise that they will only accept Bitcoins. Nothing traceable, or reversible. Does anyone else see the irony in this?

While I think a 32GH Rbox would have been a better choice (less money, less power), a Jalapeno will do just fine as an introductory Bitcoin miner. Certainly better than a GPU mining rig.

Have fun, but don't expect to get rich, or even break even.

Just to be flippant, does the above mean:

1) Don't hire employees in the first place?

2) Hire them and just don't actually pay them?

One additional thing I meant to add. While phillipma1957 is one of the most respected folks here, and his list represents  probably the best hardware available, you still won't get rich from one of the pieces of hardware he mentioned.  If you are lucky, you'll make your money back, over your electricity costs, and have some money left over to take your family out to dinner.

If your financial situation isn't such that you can see your hardware investment drop to zero value, I would discourage you from starting into Bitcoin mining in a serious way. My simplistic view is:

Don't invest anymore into Bitcoin than you are prepared to lose.

There are worse things in the Bitcoin realm than to spend $15 and realize you won't get rich. You could have decided to take a flyer and spend huge sums of retirement money on Bitcoin mining hardware.

I am sure if you had enough real money (say USD), and not just Bitcoin, you could buy them out. The you get to decide how to continue the adventure with Bitcoin currently priced at $225.

Just to be even more pedantic, I think there are some limits on how big a change there can be in the difficulty for any single change. I may be wrong on the specific of those limits, but it's already clear that it would take a very long time for it to happen. Also, aren't the confirmations of Bitcoin transactions wrapped up in the "mining process". So much for the vaunted "speed of Bitcoin" of you stop things for a few days.

This going to be interesting to watch. Depending on how you like to calculate percentages, Phillip either made a change of some 6-7%, or a 300+% swing in his thinking based on his original estimate.

Not to pick on Phillip, just that he's the "owner" of this as it were.

I got in for the grand total of about $60 back in late August, with my purchase of 3 of whatever the hashlet was they were selling at the outset. I mined some small amount of Bitcoin above the maint fees, but realized most of actual appreciation was based on the conversion of my "whatever hashlet" in to a Prime one. I got completely lost in the proliferation of the various hashlets during September, and just let things chug along. I never really understood how they could sustain this model of mining Litecoin and then converting those to Bitcoin to pay me. During October I realized that all my value was actually based on the inflated value of the Prime hashlets, I sold those off during October and probably made a net of $125 directly on the sale of those. When they started to press forward with the Paycoin adventure, I shipped off my Bitcoin sitting there and let my single "gift hashlet" go along. I have no idea what it finally did over the last 60-90 days.

The early days they must have been making money hand over fist selling "Hashlet Primes" at $50 per. I don't know if it was a Ponzi scheme, or just a failed adventure. I do know that not everyone loses money in a Ponzi scheme, just those left at the end.

My guess for the difficulty increase is:

1.95%

If the price of Bitcoin remains at it's current $235, it requires extraordinary circumstances to earn a profit. This includes really cheap electricity, and/or a very cheap cost to acquire mining hardware. That's my long way of saying it's "just a bit more complicated".

It's important to note that bitcoinwisdom isn't really very accurate in terms of it's projected difficulty change right after it's changed. It could easily swing to a positive number over the next 10 days.

As has been noted before, The "turn off" of inefficient mining hardware can be delayed by a number of things. It might well be less costly to the organization to mine at a small loss than incur a bigger loss by turning off a miner altogether.

I don't understand why you would ask the question if there isn't a real profit motive in your mind. While it's all well and good to have an interesting hobby, and want to "support the Bitcoin network", it doesn't really mesh with the question.

With a consumption of 3350 watts for 7000 GHash, that's pretty efficient. Your bitcoin earnings will exceed you electricity cost for quite a while (say 6 months). You didn't say how much it will cost to acquire this mining capacity, so it's impossible to know if it will pay for the acquisition cost or not. You might want to consider:

https://bitcoinwisdom.com/bitcoin/calculator

Alas this is not be. I got an E-mail from Zoom Hash less than 48 hours later saying that they had to cancel the order. So my "S5 for $348 shipped to Minnesota, paid with Discover" turned into a flop. They are crediting the money back. Bummer.......