Maybe set up some scripts to e-mail his work/home e-mail address every few hours or so.

Adopt some spamming techniques to get past his spam filters.. random words from a dictionary.

IM bots too, so when he comes online he gets slammed with "Why did you take my money" IM's.

Got his cellphone number? I'm sure there is a way to text message it. It probably has an e-mail address.

There are other shadier things I'm sure you could think up.