And apparently the sky is falling. From Ittay Eyal and Emin Gün Sirer at Hacking, Distributed:
But the fact is, this is a monumental event. The Bitcoin narrative, based on decentralization and distributed trust, is no more. True, the Bitcoin economy is about as healthy as it was yesterday, and the Bitcoin price will likely remain afloat for quite a while. But the Bitcoin economy and price are trailing indicators. The core pillar of the Bitcoin value equation has collapsed.
They note previous bad behaviour from GHash (which GHash attributed to a rogue employee).
Their proposal is a hard fork, with different parameters (to make huge mining pools no longer an economically rational choice), but respecting the blockchain to date so they can reasonably keep calling it "Bitcoin".