It's very hard for me to pick out a drop of water once it lands in the ocean.
Lucky for us, bitcoin is not water and our wallets are not an ocean.
With coin control, we can achieve zero capital gain/lose on our day-to-day expenses, recognizing taxable events in lump sums using an automated coin swap (mixing) service. Our wallets can track every transactions so that we have rigorous proof of compliance with US tax laws. We can't do this easily
now because the wallets aren't yet available, but the purpose of this thread is to start us moving in the right direction.
Okay, for discussion purposes, and I'm really and genuinely curious about this:
A lot of people, whether they should or should not, and just because they can, consolidate their bitcoin holdings to a few addresses. With the advent of coin control, some of these people, not only consolidate different outputs to one bitcoin address, they combine several outputs into one output in one address.
When you do that, the coins are "mixed". It becomes your small puddle of water. Because all the outputs are now 1 giant combined output.
This happens, for example, if I have a lot of dust or a lot of small transactions. Let's say I have one hundred 0.01 outputs. To try to save space on the blockchain an to avoid paying fees, I combine all of those into 1 BTC.
The 100 individual outputs are no longer there. It's just one 1 BTC output.
I run a raffle / lotto, that accepts "bets" into one address, much like the classic Satoshidice used to (or still does?) What I typically do is combine all the unspent outputs into one transaction that pays out to one address their prize.
The typical coin laundry service either spits out outputs from other people. There are others that just simply combine the outputs, so it's not hidden, but the original coins are still mixed; or all coins are "tainted" the same way.
Now, maybe I understand it wrong, but combining outputs, or spending in such a way destroys the "old" coin and makes "new" coins. The individual histories of the value of the coins bought a certain points in time is now "gone." I mean, it's still there, but you can't link it anymore.
Your poll is one example, 1 BTC worth $1200 (for example, bought in December 2013 or January 2014) and another 1 BTC worth $100 (bought some time last year.) Some person decides to spend them using the two outputs and in a transaction turns it into one output now 2 BTC (with no change).
Thus my original quote.
On an unrelated note, there is a similar saying: Every single drop of rain does not think it is responsible for the flood.