What is sad.. is the number of people who tie them selves in knots trying to figure out clever ways to attack bitcoin using 51% attacks and other 'clever shit' and working out all the cost that it would entail
.
In reality it only requires an attack on the software.
All that money trapped by the FBI
it's only trapped because that is the way the software is written.
The hard part isn't changing the software.
The hard part is convincing every single node on the network to run your changed software instead of the original software.
So what is cheaper?
To 'convince' Two BIG mining pools to change the software or to spend hundreds of millions masterbating about designing a new ASIC?
Not "Two BIG mining pools".
"Every single node on the network".
If "two big mining pools" change, they'll be mining something other than bitcoins. All the other nodes on the network will refuse to relay the blocks created by the "two big mining pools". The total hash power left on the bitcoin network will drop and the remaining pools and miners will all earn twice as much bitcoins as they previously were.