often a force quit is the only reasonable way out. but then safari likes to reopen pages when relaunched. turning off javascript seems to be the best way to deal with them sometimes.
I looked at scam zapper, hoping it was something that would detect the lock-in windows themselves, but that doesn't look like what it's doing. It appears to have a blacklist of known URLs that host them, and so it only works for sites in its list. That's not nearly as useful.
