Here's an interesting bit from Homeland Security Secretary Janet Napolitano's interview with CNN (small segments of which have been televised throughout the day) in which she says the Christmas Day attack shows the threat of terrorism to be different--more discrete, prone to more isolated attacks--from how it's previously been envisioned. Transcribed quickly from CNN's airing:

"It has changed. The typical kind of assumption on the threat was sort of a large [conspiracy] 9/11-style attack. What we saw on Christmas was an individual who comes out of Yemen who's been radicalized, who gets into the travel system, dots are not connected in the intelligence community--and that's what the president has ordered to be addressed and rectified--he gets through the screening done at Amsterdam, and...that's a much more different threat, in a way, to deal with than a conspiracy where you have multiple ways to intercept communications and the like, so I would say that it's a changing threat and perhaps a more different threat," Napolitano said.