My first guess would be that is the BTC that Karpeles stole.
not sure what you're referring to. you mean the guy Kevin who stole around 2000BTC?
Although the evidence is circumstantial, a plausible case can be made that the great bitcoin theft actually took place in 2011, and all the following events were the result of Mark trying to fix it:
http://www.reddit.com/r/Bitcoin/comments/1zdnop/peter_rs_theory_on_the_collapse_of_mt_gox/
I've always liked that theory, *except* where is the ~1,000,000 BTC transaction (or handful of transactions adding up to that) in mid June 2011? (note: I've never bothered to look, but never heard anyone mention their existence, either).
Sidenote: It was the rebound from $0.01 to ~$17 after that hack that gave me enough confidence in the bitcoin economy/userbase to make my first purchases and sign up here. And I remember watching those penny trades in real-time. Crazy.
yeah, while totaling those volume bars during few days is difficult, i don't see evidence of 1M BTC traded during that time.
btw, the current pullback was a result of Gox also. it's a good thing they're out of biz: