[tafreeh]

I get those too.. Here is a solution from me:

Create a new usergroup for user whose post counts are between 0 to 20. and disable Signature for them. A real looser will still make 20 post and then put a link in sigg, you can delete that too later on

By doin that you will get two benefits (1) Discourage Spammers (2) along with signature you can offer other options too so das how you will courage users to post.

It almost reduce 90% of spamming at my forum tho.. I do like your idea too.. but I will still have to check my emails and go to admin cp and edit or delete their sig then banned.... thats too much hassle