How close do you live to him? Visiting his house wouldn't be a horrible idea, but you may get busted committing any fun acts of vandalism.
Some other ideas: anonymously call his workplace every 30 minutes telling them to fire mr. x for being an identity thief (using a payphone or voip). Get his parents' info and call them as well, telling them the same thing.
Wearing latex gloves, put some child pr0n on an envelope and mail it to him using his own address as the return address as well. With any luck, a bored postal official may open it up. Make sure to do it somewhere close to where he lives for better effect (so the post office doesn't dismiss it as a prank right away when they see that the return address is in the wrong region).
Send him all the DHL shipping supplies you can order, every three days.
Sign him up for every junk mailer/catalog mailer you can think of along with magazine subscriptions . Have every branch of the military call him for recruitment, as well.
