A few minutes before the rally started nearly all the bids on Bitstamp down to 360 were removed within in a second. Also quite a lot of asks were removed, but far less than bids. I switched over to the trading PC and by then everything was back to normal. Did anyone else catch that? I wonder what that was all about, there were literally only a few dozen coins worth of bids down to 360, basically just a long flat green line (on bitcoinity.org). A bug maybe? But would be a weird coincidence because it happened right before that rally.
About the rally itself: I kinda feel that this was orchestrated by a single entity, probably in order to induce a short squeeze. I doubt very much that this was "organic" buying by people who suddenly all decided to buy in unison. Or maybe I'm wrong and it was caused by a bunch of people buying because of the paypal news, but I doubt it...
I followed the rally early on and decided @ about $415 that someone was trying to squeeze those 11000 shorts out. So I went "picking up pennies in front of the steamroller" - I bought into the askwalls, then set up my own askwalls at a slighty higher price. Worked out well, but I would have been in trouble if the price had reversed suddenly. Bids were very thin, so I wouldn't have been able to sell the coins back at the price I bought them at. Was probably not a good idea, even though I made some profit.
Similar to my own ideas: I don't think it was "organic" either, in the sense of buying pressure slowly building up, then being released. Looked like a single entity to me as well, only question is: why? Seems by buying gradually, you could minimize slippage, so assuming the original assumption (one entity driving this one) is right, I can see two reasons to buy it all at once, across exchanges: to "make a point" for the bulls, or to squeeze shorts. The latter didn't seem to work (so far), however, judging by the finex stats.
This was clearly a bug at bitcoinity, happens a lot. Their bids/asks live chart for stamp is so unreal and not realiable to monitor lively and track changes. You need to use stamp order book chart to help with it to see how things really stands.