What always surprised me most is the general acceptance with which the dwarven and elven settlements accept outsiders to walk amongst them. Dwarves and elves tend to be very xenophobic according to everything I can remember... I always thought those settlements should have locks on the doors with guards, only allowing access to proven friends (given by DM quests, etc) and giving more reason to want to go there (maybe with a revamping after it's been closed off.)
I don't see any reason to make them sinkholes in order to spice them up, to me that seems boring... there are plenty of other things that could be done to create springboards to adventure with them.