Yeah the answer is technically correct in the general sense.  Double hash is a useful cryptographic feature to prevent extension attacks.  The author of that answer may not have been aware that Bitcoin has a fixed size header.

The generation (block reward) tx has a single input.  Normally the input of any tx is the unspent output of a prior tx however generated coins are produced from "thin air".  The input is a special type of tx called the coinbase.   The Bitcoin network doesn't use the value in here for anything (although it is now used by subordinate chain in merged mining).   Miners can modify this to produce more possible block headers for the same set of inputs.

So say for a given set of transactions, time, prior block, and difficulty you try all nonces 0 to 2^32-1.  What can you hash next if you don't want to wait for any of the other values to change.  You simply change the value in the coinbase field to another value.  That will produce a new merkle tree and thus a new markle root hash.  Technically it doesn't need to be incremented any new value is fine but for simplicity and record keeping (pools) it makes sense to just increment the value.   Pools do this to issue work to multiple workers that are otherwise the same.   solo miners will need to increment this if they have a hashing rate greater than ~4GH/s.

hash extension attacks are only possibly on arbitrary sized message.
Bitcoin block headers are fixed size.  A valid block header must be exactly 640 bits (no more, no less).

Hmm.  Never thought about that angle before.  I mean for 99% of programmers all these endian conversions just make the code more confusion to understand however for some programmers it might be second nature.

Then again there are a lot of other "quirks" which are equally hard to explain.

Why use 32 bit nonce + extra nonce?  Why not just use a 64 bit nonce?

Why a double SHA-256?  If the fear was that SHA-256 would be partially compromised one would gain some security by using two algorithms but you don't really gain much performing the same algorithm twice.

Yeah I forgot Satoshi for some reason messed around with the endianess of each 16bit bit portion of the number.

12345678 -> 12 34 56 78 -> 78 56 34 12 -> 78563412

So
42a14695 -> 42 a1 46 95 -> 95 46 a1 42 -> 9546a142

They haven't "done" anything.  It is called hexadecimal.

Reese it has been tested in court.  I found 38 notable court cases in the US related to the enforcement of "digital signatures" since 2005.  The actual number is probably significantly higher, the legal search tool I have access to has limited coverage.

Also under US law your signature above wouldn't be considered a digital signature in any of the 50 states.  It would be an "electronic signature".  Please cite a link that shows the EFF is opposed to the enforcement of digital signatures.

It is an interesting idea.  Since you are already a registered company (LLC, Corp) I would make sure in the contract that you aren't offering equity in your company but rather offering "shares" of a revenue sharing contract.  Also be sure the contract clearly explains that revenue and profits are in USD. GLBSE needs more real investments and could potentially be very useful for companies to raise "non traditional capital".   would recommend you take your time.  Launching quickly with a poorly worded contract is likely going to reflect badly.  Find someone with experience on GLBSE have them look over your draft contract, make suggestions/revisions.  Release the contract and asset terms will in advance of the IPO day.

I will be following this closely.  As an owner of a US based company we are considering setting up an offshore holding company which would be sold a fractional ownership stake of the parent company.  Your success here will be a good predictor for our potential success.

Maybe the theft was reported AFTER A sent the coins. 

A accepts coins from thief (unknown to A).
A sends coins to B
blacklist updated to include theft
B client reports coins are tainted.

So who gets stuck with the blocked coins?  A? B? It certain isn't the thief he already got away with it.

Your right that it is voluntary but it many believe it will be conterproductive and create chaos and additional risk.

Just some scenarios you may not have thought of:

Say I accept coins from someone and then the "bad tx" ends up on a blacklist?  So now through no fault of my own I am stuck with coins that I may not be able to spend.  At best I lose some % of their utility, at worst nobody takes them and the cost of the loss is passed from the responsible party (the thief & the entity who left coins unsecured) to me (an innocent third party).

Think that is going to increase merchant adoption?  What about malware?   Infect user's computer so their black list is spoofed and trick them into accepting "bad" coins.  

Also what about coin "hostage".  You sell me 1000 BTC worth of Gold.  I pay you 1000 BTC.  I then say I am going to report these stolen unless you give me back 100 BTC.  Your choice lose 10% or lose 100%.

The person(s) maintaining the list?  How are they going to pay for the cost of investigating all these claims and counter claims?  Charge list subscribers?  So the loss is simply subsidized by third parties.

You can't pretend it is all benefit with no cost.   The cost is in terms of confusion, chaos, complexity, reduced adoption, acceptance risk, and corruption (lots of power & money to be made adding/removing an address from a blacklist) are huge.   You are right nobody can prevent you from building a list today but it doesn't mean that it is a good idea or people won't do everything possible to ensure it doesn't gain enough acceptance to be effective.

BTW: Not sure where you get the idea your proposal is new.  It has been proposed before many many times (essentially once or twice after every major hack going back 2 or 3 years).  It is just as bad now as it was when first proposed.

You do understand that will result in transaction fees?  So you willing to pay it out of your own pocket?  

Also if the client has the ability to sign tx then the wallet is unlocked.  You like the idea of your wallet being unlocked 24/7/365 in order to return coins you don't "like"?

No. 

A tx consists of inputs and outputs.  Unspent outputs becomes the inputs of a new tx. 
The tx is hashed and the hash signed by the private key of the address the unspent outputs were sent to.

Nobody can answer that exact question.  The IRS can do just about anything it wants.  Then again the IRS has roughly 700 million tax returns (resident, foreign, business, trusts, etc) to process and verify every year.  Plus they need to track down tens of millions of delinquent tax payers owning trillions of dollars collectively.  Add to that the filing and responding to hundreds of thousands of lawsuits each year and you can imagine they got a lot to do.

The simple solution is to just pay the taxes.  Not sure what you are doing (and honestly I don't want to know, seriously) but the IRS doesn't care if your business is unlawful as long as you pay your "fair" share.

Still in all honesty your $30,000 per year is "chump change".  I mean if your marginal tax rate is 15% we are talking about $4,500 in additional taxes.  If you make less than $100K per year the odds of you being a target of an audit (due to return being flagged) is essentially 0%.  Now in addition to targeted audits the IRS does randomly audit about 1% of all tax returns.  If you are audited due to bad luck in theory they could pull your PayPal (and other financial) records and ask you to explain.

Simple version:
The lower your income the less likely the IRS is going to look.  You don't have as much ability to pay, you likely have less assets they can use as leverage, and the amount you can evade is directly related to your income.  Catching one $10 mill tax evader has a higher ROI% than trying to track down 2,000 people who evaded $5,000 in taxes.

That isn't exactly correct.

Any breaking change must be supported by EVERYONE.  Users, miners, exchanges, merchants, etc.

So if 51% of miners implemented that change those who disagreed could continue to use the "old/existing" Bitcoin where miners can't steal 10% of all coins.   The 51% of miners would simply be mining worthless blocks which have no value.

As long as some users and miners continue to support the current protocol it will exist.  What gets kinda meta is what is Bitcoin.

Say some miners decide to fork the protocol to keep the block reward at 50 BTC.  Since this is a breaking change it doesn't really matter if 20% of miners support it, or 80%.  The "51% check as in 51% attack" doesn't apply since each version of the protocol sees the other as completely invalid regardless of how much mining power supports it.  Now lets make it extra confusing. Lets say roughly half of the users support this change and upgrade their nodes but roughly half don't.  Some merchants support the "old" coins, some the "new" coins, and some support both (by implementing both nodes).  The same applies to exchanges.

Essentially at this point you have to completely independent protocols.  Which one is Bitcoin?   Obviously both camps will claim they are the real Bitcoin.

Technically there is nothing which can't be changed in Bitcoin.  Bitcoin is what a consensus of users say it is.  That being said there are many thing which will likely never acheive the necessary consensus for a change.  

Bitcoin will probably never:
a) be reversable
b) support a proof of stake
c) have an incompatible mining rate
d) implement some mechanism of recovering "lost" coins.

While in theory these could be changed they are simply too controversial to generate a consensus.

IMHO there are very few limitations of Bitcoin which can't be overcome with:
a) third party services.
b) extension of bitcoin protocol.
c) extension via higher level protocols which are built on top of bitcoin infrastructure.

Why would it be replaced instead of just updated/extended/patched?

So what has replaced the internet (TCP and IP protocols)?  They have a ton of flaws & shortcomings.  There are lots of things which could be done better if you replaced everything from the ground up with a new set of protocols.  The internet looks nothing like the internet of the early 1980s but the low level protocols are still there. They have been extended and upgraded but not replaced with a brand new system.

Did I miss the memo where we just ripped up the entire internet and replaced it with something new?

LOLZ.  US owns most of US debt.  Try reading more than the headline next time.

Well you didn't do everything.  The terms and conditions you agreed to were that the exchange could require verification of any asset owner for any reason.  You didn't. The terms also gave the exchange the sole discretion in approving a new listing.  They didn't.

The fee was non-refundable and you new it was non-refundable.

Why would refunding a non-refundable fee be the right thing to do? 

Why wouldn't you get your interest payment?  With average of 0.7% daily interest even if nobody else bought a single share he could pay you for 142 days just using absolutely nothing but the "principal" you gave him.  It would be utterly shocking if you DIDN'T get the interest payment on time and in full.