Yeah, usually nothing you can do about it directly. However, there is a nice theory on fighting spam that I read a few days ago on silenceisdefeat.org.
http://silenceisdefeat.org/~samble/spam.txt
Sort of has similar in theory to a DDoS, except the goal isn't to cause any harm to their server or anything of the sort, but their wallet. After all, they're paying money so you can click their links, so might as well give them what they paid for. This should make their costs go up enough to either a) force them to stop spamming their products, at least in those amounts or b) having failed the first option, run them out of business.