Having recently wanted to cancel my subscription to a few wayward threads, I was feeling too lazy to click my way through to my profile and delete the thread from my subscriptions list.
How about a simple Quit Subscription button on each revisited thread? I've seen it on other sites too.

Tch tch tch - lazy, lazy, lazy!

Sounds like a good idea... but what if something worthwhile get's posted?

See! This is exactly the sort of thing I had in mind!