The solution to “follow spam” on twitter is simple:  

Like everyone else on twitter, I get multiple “spamtastic moron is now following you on twitter!” email notifications daily. There is no easy way to know whether or not these are person who want to follow me from one of my site or from some twitter “conversation” they read… or if it was just another twitter follow spam.

Facebook gives you the ability to send a message when you add someone as a friend. A simple, “hey, it’s me, I’m the person who ____” message that could be added to the email notification would completely solve the problem of whether or not to follow someone back.

Stopping spammers from trying? Good luck on that! ;-)