According to Bruce Schneier, author of Schneier on Security, the TSA is useless because:
" . . . if a group of well-planned and well-funded terrorist plotters makes it to the airport, the chance is pretty low that those blue-shirted, crotch-groping, water-bottle-confiscating TSA agents are going to catch them."
Well said, Mr. Schneier. Well said, indeed.
(Source: Bruce Schneier's column
"Why The TSA Can't Back Down", The Atlantic)