So... when you click the "(un)subscribe" link:
If you are already subscribed, unsubscribe.
If you are not subscribed, subscribe.
Totally possible... I'll add it to my to-do list. I'd like to code it right now, but I don't have time.
That would be kinda cool if the link text actually changed to show whether you're subscribed or not, but it's a little extra work for MySQL... I'll think about it. As Cookie said, it would solve the "accidental subscribe" issue...
The suggestion for checkboxes on the subscription list is good too... I always thought the individual "unsubscribe" links were kinda crappy.