Krypsyn: While it is true that Mafia could easily use one player to "reset" the block-out on their scumbuddy, or otherwise use the fact that they are teamed to their advantage, I don't think it would be smart for them to overuse such an ability.
Oh, I was making the opposite point. I don't really see a tactical use for scum that's meaningful since they'd only target a teammate with the intent of moving off (unlikely to bus with 2, but possible). Possible that waiting too long locks them out, but they'd have to misplay to get there.
You're right that they could tactically unlock, but in the scheme of things that's pretty minor.
Imagine I'm town and you're town. 5 votes are on the table (or deadline approaching) and one of them is me on you. Say I either realize through the course of conversation you're town or that drealmer is scum and want to switch my vote to drealmer as the better choice. But I unvote and have to wait for someone else, and say either votes 5/6 come at once, or deadline comes, or no one votes and I have to log and it's closed by the time I'm back, etc.
Town can't really "plan" for when enlightenment will come. Thus the mechanic gives them a slight penalty that scum doesn't really have. But with 8 town and 2 scum, if anything it probably moves slightly toward balance rather than away from it.
If it were 7/3, then I'd be more concerned.