According to the Congressional Quarterly Jeff Stein, the FBI hoped to track down Iranian terrorists by following, out of all things, Falafel sales in groceries.
The photo on this story at Wired blogs, shows Iranian dishes.
What is sad is that falafel is not part of the Iranian cuisine, being mainly a staple of the Eastern Mediterranean.
They are delicious for sure, and I have them all the time ...
Also see this Slashdot discussion.
The FBI denied that such a program existed.