If its an e-mail address, change your e-mail address, block them from sending you mail.
If its snail mail, mark on the envelope:
Return to Sender
Address unknown
No such number
no such zone.
I did sign the petition and just delete the e-mails. The presses put the e-mails out there for people to comment on. It's just you get a few wackos out there. I think it's quite amusing.