Pardon me, the word 'could' was missing, distorting my intended meaning. Edited.
I claim that the for the purposes of criminal activities the existing more popular electronic currencies are just as effective as bitcoin would be.
Now that you mention it I would claim that criminals use anonymous online currencies. Online currencies are notorious for money laundering. I have no idea what terrorists in particular currently do. Just what online resources they have available.
Now you can donate to Singularity Institute using Bitcoin.
Currently Bitcoin mining appears to be profitable as only bubble economics can be. Already some Less Wrong users have purchased GPUs and started mining Bitcoin. Please consider sending some Bitcoins to SI at address 1HUrNJfVFwQkbuMXwiPxSQcpyr3ktn1wc9
2014 Edit: Please donate Bitcoin by using the Bitpay link on MIRI's donate page. Thanks!