I got my first dosage of pharmacy spammers, and they came from an email address with the .ru prefix.
This made me ask, what email addresses should I ban from registering?
I dont want to get to deep with banning things like GMail and Hotmail
It's not what you are asking, but I've cut most of my spam traffic by banning one single ISP in Moscow: mtu-net.ru. I have no explanation why this particular ISP sent me all spammers, but this worked out very well for me. You may give it a try if you don't expect users from Moscow on your website.