Most likely source of the major dumps?

[rebuilder]

How many people have records of how much BTC they bought and when? What documentation will the IRS accept?

With Mt. Gox, if I remember correctly for 2011 tax year the account holder could request that an IRS 1099-B report be generated for them.

That's good, I guess. Any idea how that works, more specifically? If you spent X USD over a year, at varying prices, and sold a portion of what you've bought, what will your buy-in price be counted as?

[DeathAndTaxes]

How many people have records of how much BTC they bought and when? What documentation will the IRS accept?

With Mt. Gox, if I remember correctly for 2011 tax year the account holder could request that an IRS 1099-B report be generated for them.

That's good, I guess. Any idea how that works, more specifically? If you spent X USD over a year, at varying prices, and sold a portion of what you've bought, what will your buy-in price be counted as?

In other assets you either need to show proof of the exact unit being sold or they are treated first in, first out.

Now technically if you didn't use a shared wallet, and only sent funds to MtGox when you intended to sell the entire batch you could (through coin selection) choose which coins to sell and thus pick your basis.  Not sure I would want to be the one trying to explain all that to the IRS for the first time so FIFO is likely your best bet.

FIFO - First In First Out.
Buy 100 BTC @ $5
Buy 100 BTC @ $7
Buy 100 BTC @ $9
Buy 100 BTC @ $11.

Sell 250 BTC for $13. 
The Basis for the 250 BTC is (100*5 + 100*7 + 50*9)/250 = $6.60.
Gain is ($13.00 - $6.60) * 250 BTC = $1,600.

Note in any capital gain scenario good records are required.  In the above example your remaining 150 BTC would be 50 BTC @ $9 and 100 BTC @ $11. You would need to keep a running tally of all purchases, date, and purchase prices, then all the sales and which (in order) basis they used. 

The good news is there is software like gainskeeper which does all this for you in equity txs.   If Bitcoin gets big enough I am sure they will add a BTC module.

[rebuilder]

In other assets you either need to show proof of the exact unit being sold or they are treated first in, first out.

Now technically if you didn't use a shared wallet, and only sent funds to MtGox when you intended to sell the entire batch you could (through coin selection) choose which coins to sell and thus pick your basis.  Not sure I would want to be the one trying to explain all that to the IRS for the first time so FIFO is likely your best bet.

Not wanting to be the first to try it out is part of why I don't see myself selling any time soon... I figure I wait until I can either just buy something significant directly in BTC or until the profits are sufficient to justify hiring a lawyer to deal with it. Probably the former.

edit: and I should note, I'd guess a lot of big early adopters are thinking along the same lines. Although Sirius apparently bought an apartment. Maybe he'd have something interesting to say on the subject.

[ElectricMucus]

I just see a minor dump, not even worth dramatizing. Considering the upward momentum not even a dump at all.

[mb300sd]

Damn it people.. stop taking dumps, or at least do it in your own toilet 

[tvbcof]

In the U.S. there are big changes coming to the tax rates.  

So if you are in the U.S. and reporting your capital gains on your taxes, it is better to cause that transaction to occur in 2012 while the rate is lower.

How many people have records of how much BTC they bought and when? What documentation will the IRS accept?

I got almost all of my BTC from Tradehill and kept a dump of my activity.  Will the IRS by happy with that?  Dunno.  Will find out if/when we get to $100-ish/BTC and I recoup my USD outlay I guess.

[smoothie]

Damn it people.. stop taking dumps, or at least do it in your own toilet 

DUMPTA DUMPTA DUMPITY DUMP WE ARE GOING TO TAKE A FAT DUMP! 

[zoinky]

Please dump more

[hahahafr]

1st wave: thieve selling stolen coins because he sees that we are gonna stay at $13.x for a while.
2nd waves: panic people.

[b!z]

Someone with no agenda just trying to sell their bitcoin is likely the most common reason.
There may be someone with many coins from a long time back, who just needs money fast.

[TraderTimm]

I think it is just regular market activity. Some of the dumps pushed a few resting order triggers, as I was watching the raw price feed stream through. That is what it looked like to me.

As far as Mt. Gox being manipulators, they'd make far more money taking a slice out of the bid-ask spread than dumping lots of coins. Doesn't really make sense to push large amounts when they can get a non-disruptive income stream the other way. (Much like how Forex dealers make their money.)

I don't think they are, but it would be the easiest way to take a cut on top of the usual 'clearing fee'.

[xxjs]

What I have noticed, is that after a dump, new buy order creep in over the lowest prrice.

So, when it is a thin buy side and a have a few hundred to buy, I put them on buy at a quit low price. Suddenly someone comes from nowhere, diving down to my bid.

So instead of waiting for the price to go low, why not place a low bid? Corresspondingly on the sell side.

[muyuu]

What I have noticed, is that after a dump, new buy order creep in over the lowest prrice.

So, when it is a thin buy side and a have a few hundred to buy, I put them on buy at a quit low price. Suddenly someone comes from nowhere, diving down to my bid.

So instead of waiting for the price to go low, why not place a low bid? Corresspondingly on the sell side.

Because then you are beaten to the punch, obviously. Do you expect bulls to tell you exactly what cards do they hold so you can beat them?

[disclaimer201]

Christmas shopping