[NewAccnt]

Rumor has it that Butterfly has been sitting on their preorders and using it to build a massive ASIC fleet. Whether or not these are true, as you suggest, building a 51% fleet is not out of reason if you take the right path and keep your mouth shut. There has already been forks of the blockchain due to powerful miners.

http://mineforeman.com/2013/03/14/what-the-fork-was-that-a-f...

[mrb]

These forks are not caused by powerful miners. They are caused by miners mining 2 blocks almost at the same time. And the fork of March 14 was caused by a bug.