(In case you didn’t pick up on this, the OP in this thread has vanished completely, so we’re just hijacking an empty thread.)
Using a made up SSN is probably not a crime, in and of itself, but one would have to assume that the only reason to use a bogus number would involve some attempt to evade taxes, or to collect benefits to which one is not entitled, and those activities certainly are criminal.
I was referring not to using a made-up number, but to using an imaginary number, like the square root of a negative number. Or maybe using a number like pi. Maybe that’s what jimbino was trying to do when he attempted to start this thread, and his post, as a consequence, simply winked out of existence!