For the last week, I've been running an experiment wherein I am clicking every "remove me" or "unsubscribe" link in the copious spam I receive. My thinking is that I already get a ton (around 100/day) and this could only help. Anecdotal evidence from others who have tried the same thing seems to point to at least a temporary reduction in spam after unsubscribe attempts. It is interesting (where "interesting" here means "not very surprising") to note that at least half of the unsubscribe links go to the same set of pages, a good percentage of those left are dead links, and the rest don't have links at all.
I'll follow up when I have any results, whether more or less spam.