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.