I think that theory warrants about as much consideration as chemtrails.
Regardles, I wouldn't exactly put it past the TSA to make up a positive hit. It's not like we haven't ever had a police officer claim someone committed a traffic violation on someone based on appearance and ultimately find drugs or some other criminal behavior.
In the past two months, I've had pat-downs in DCA, BWI, and PHI (my home airport, SYR, doesn't have scanners, so there's nothing to opt out of).
They all use machines similar to this one:
http://www.tsa.gov/sites/default/files/images/edt_closeup.jp...
I've never seen a failure myself (the green bar you see pops up after a few seconds), but according to a friend who has, a red bar pops up instead.