I've seen a lot of minor reasons why it dropped but the real reason is obvious. The distance in time from when GPU mining really took off to about a week ago is approximately the time it takes to pay off the average efficient set of cards. If I mined from April to now, my cards would be paid off too. So people with lower budget simple rigs are hitting that level and thinking about selling for USD or permanently withdrawing their USD from the exchange so their long term investment ends nicely instead of continuing to risk it.
The majority of miners joined to make money/get "free" cards so if you've made around the cost of your rig and saw the price drop and stay there for a few days then sneak down a little more then stay there and show no sign of raising but you're sitting on like 30-50BTC, you're going to take the opportunity to dump them all on the market just in case it drops to like $2 and ruins your entire mining experience.
Unlike other people, I'm going to actually post evidence. 2 months ago there were about 8 radeon 5830's on ebay with the cheapest at $140. Now there's 38, almost all used, almost all referencing bitcoins, and the cheapest around $127. People are definitely selling off their rigs now that the price dropped and they've already "cashed out."
What's not causing the drop is:
- investors because no investor sees it drop like $2-3 and decides to sell. That doesn't make any sense and if they're as stubborn as me, they won't sell it at a loss even if it takes 6 months of sitting on BTC to prevent it.
- any blog post, news article, or forum post caused it because our opinions on BTC is pretty set in stone and can't be shaken by something so insignificant.
- a massive theft and sell-off because we should have heard about it by now. It would have been at least like 500,000 BTC to get to this price and that's almost 10% of all coins that exist.
It has nothing to do with trending, or charts, or investors, or lack of interest, or too much interest, or anything logical that would drive a BIG market: It is just a bunch of crooks cashing on their loot, at whatever price. PERIOD.
Now, if we take into consideration that these crooks have dumped MASIVE AMOUNTS of bitcoins in the past few days / week, and the price STILL manages to hold (I know it went down from $12 but please follow me), in an economy so small, the fact that the price is holding, even with people dumping large amounts of bitcoins with little regards to the price: that says something good about bitcoin, and the bitcoin economy.
Imagine some crook gets ahold of 2 million microsoft shares, and starts dumping them and dumping them, without *much* care for the price. MSFT goes down, but doesn't collapses, stills finds buyers, still holds. So there you have it. I think bitcoin will get out of this one if:
1. People start protecting their wallets and blindly trusting anonymous services (because if you are dumb and get robbed, you are really hurting us all, the bitcoin economy that is).
2. People don't panic and start selling like sheep.
My 2c