yeah, sign him up for every sort of solicitation you can imagine. Not just email. Look up the church of Mormon and indicate that he's interested. In addition to mass mailing him, they'll have someone come out and bug him just about every week (assuming there's a church of Mormon in AU). I'd do that for any and every church that you can imagine.
Sign him up for the NAMBLA newsletter (I'd do it from a proxy, though. Look around here for how to browse anonymously)
Use his email address to do "free Ipod, free car, free *) surveys and request information from everyone listed. Give both his phone and email address. And home address, too.
If you really want to get him in trouble with his parents (assuming he's also younger) you can sign him up for mail order bride catalogs to be sent to his home (someone did this to me a long time ago and my mom was pissed for weeks).
Or, one of my favorite pranks:
Call up 100-200 people and say:
"Hi, this is *victim's name* and you just won 1 million dollars! To claim your prize, call *victim's number*"
Of course, maybe only 1% of the people will think it's legit, but if you make like it's a prank (and are really loud and obnoxious about it), most of them will call the number just to bitch him out about solicitation. Better yet, if you can use Skype, freecall, or just plain caller i.d. spoofing, you can make your calls come from ANYWHERE!
one of my friends did this to me for my birthday once, and the results were fantastic; I got calls about this for a week. We repeated the prank large scale (we called nearly 1,000 people) and had them call a cell phone. I think our victim's parents ended up getting his phone shut off because of all the minutes he burned up just answering the calls.