This follows the four failed attempts yesterday.
I have the feeling that the security forces have been getting some very good information through (being on two trains that had bombers/suspects for instance) and maybe some inside help (bombs not going off due to failed detonators) as well as a heightened awareness yesterday before the bomb attempts in the first place.
I also loved the !Keystone Jihad" comments I saw on a friends journal.
Good name for the ineptness of yesterdays attempts anyway!