[EricE]

They could revoke the land line companies authorizations too.

The problem is it's a complex issue affecting millions if not billions of what is now legacy phone equipment that would have to probably be replaced. And for land lines that's a dying market - no one in their right mind would want to modernize infrastructure that's more than likely on it's way out. Might be able to get cell phone providers attention far easier.

Both groups have significant lobbying presences, I'm sure, so it will continue to be a pitched battle - but if it's ever going to be a traceable/solvable problem the fundamental protocols used between phone exchanges are going to have to be beefed up with spoofing in mind. Before VOIP and the number porting rules others have referenced in this thread it was nigh impossible to spoof numbers because each phone company owned their own block and that was that. Now any number can be held by any phone provider - the horse is out of the barn :p