I had a nice conversation with a woman at the FBI and she gave me a website to report the incident. The website is really intuitively named so victims of this scam can find it easily:
You can see how any one can figure out how to find that, just from it's name, can't you? NOT! TIGTA stands for Treasury Inspector General for Tax Administration. . . and that's even really intuitive to find. The FBI gal and I had a good laugh over it as well.
I played the scam guy along for a while before he hung up on me.
Was thinking about this scam ... thought about toying with them and claiming to be illegal immigrants who never paid taxes ;-)