Which is why GP said: "And if I manage to get somebody else's private key (which happens so often these days, it's not even funny), I can ruin someone else's ca

Which is why GP said: "And if I manage to get somebody else's private key (which happens so often these days, it's not even funny), I can ruin someone else's career while I push my spam." Also, the biggest problem with PGP-type signing as a mechanism to control spam is not whether you can spoof the signature or not, it's that there's nothing in it that stops the spammer from generating a new identity once the current identity is tarnished.