Remember the Great Anarchist Plot to Blow Up a Cleveland Bridge? Sabrina Rubin Erdely has a great piece in Rolling Stone on the case [pdf], taking a close look at the unhappy, alienated people who got roped into the plan and at the FBI informer who organized everything.
When you're done reading it, you can compare Tom Junod's similar story about the "Waffle House plot" in the rural South. The agent provocateur in Junod's story worked for the DHS instead of the FBI, and the people he entrapped were angry old right-wingers rather than angry young left-wingers, but under the surface it's a strikingly similar narrative. After that, take a look at any of the alleged jihadist conspiracies—here's a recent example—that followed the same basic outline. Apparently, there's a lot of federal officials who think the easiest way to foil a terror plot is to cook it up yourself.