I use my bandwidth to cost people who host "Flash Updater" Trojans money. When you find a site with a downloadable Trojan, just run a download script which downloads in a loop a hundred times simultaneously.
I'm very public about it:
https://twitter.com/AnachronistJohn/status/12343139528652144...
I do hope someone reports me, because if they do, then I'll know who they are. So far, I've cost one scammer close to $2,000 before their links died completely.