The FBI and I don’t know who planted the bombs in Boston.  Nor does Susan Collins, Senator from Maine.  She, however, is willing to speculate (from Dave Weigel at Slate):

“Whenever we have an attack like this it’s difficult not to think that it’s somehow involved in Islamic extremism,” said Maine Sen. Susan Collins, until recently a top member of the Homeland Security committee and still a prime mover on security bills. “I don’t have evidence to back that up. That’s just based on previous attacks.”

This is really dumb–“based on previous attacks” is evidence.  Really bad evidence.  Via Ballon Juice:

Except maybe here, here, here, here, here and here.

Maybe there ought to be some kind of history test for Senator.