Jonah's right, Janet Napolitano should start looking for new work. Sure, an underwear bomber* probably would have slipped through just about any airport screening, but her assertion that "the system worked" after the fact was absurd.
Add it to her other gaffes, including her assertion that the 9/11 attackers entered the US through the Canadian border, and her memo on the danger posed by disgruntled veterans who have fallen in with right-wingers, and her continued insistance that DHS is essentially a clean-up crew more than a preventive agency.
Janet Napolitano is a (wo)man caused disaster all her own, and she should be scuttled.
* (It has been suggested that the underwear bomber be called the "eunuch-bomber", a play on UNIBOMer. I support this designation, if only for the rhetorical demasculinization of individuals eager to see 72 virgins.)