I came across this on Wired’s Danger Room:
Night-vision goggles, armor vests, F-14 fighter components that could only be used by Iran — these and other sensitive military items, some stolen from the U.S. military, have been purchased by undercover government officials . . . on Craigslist and eBay, according to the Government Accountability Office.

The vests and goggles you can buy through the civilian market. These are classified only because somebody wanted to try out their brand new “classified” rubber stamp.
However I would imagine that if you could arrange delivery of any F14 parts to an Iranian embassy or consul you would make a rather nice profit.

Some years back 60 Minutes did a piece on government auctions. One company built a Cobra attack helicopter for use in the movies from parts obtained through auctions. Including, if I recall the story correctly, the missile guidance system.
This part is still a highly sensitive item that was not stolen, but made it’s way into the system and was purchased by an honest company at an open auction.

I wonder how many classified parts are actually sold every year and how many find their way into the wrong hands.

And if the F14 has been retired, why do we need all those spare parts?
It’s not like we have a shortage of warplanes in the arsenal.