350k BTC seems to be an insanely huge number.

Fuck it, even 120k is an insanely huge number for a simple website like satoshi dice. That's 1% of all current bitcoins for a concept that anybody can copy

I see it the same. For this reason, I'm beginning to favor this scenario:
https://bitcointalk.org/index.php?topic=258066.msg2751829#msg2751829The buyer may well be an established online casino. That would be actually good news, SD needs some big improvement.
Its also possible they have been accumulating, the BTC sum they need is big.