Sign them up for a 100s of magazine subscriptions. Use your imagination on which ones to pick. If you know their email address and possibly their phone number, start signing them up for all kinds of info and subscriptions providing their email address and phone number.

Internet surveys are a great way to get their email, phone and home or PO Box address broadcast so they can get as much junk mail, sales calls and spam as possible. They'll never know where its coming from and I don't think you've committed a crime. There are all kinds of "free trial offers" (google it) where they could have all kinds of stuff arriving at their door, etc.