I think it's a good thing to have many people in the pot if they are loose fish, if we can be confident that 2pr, if we flop it, is likely good. I know it's usually good, but not always. It's good more often to flop aggression against he who plays top pair/overpair like the nuts. Again, I refer you to their tendancies. Pick your opponents well.
Pockets, we tend to want a lot of callers with small pairs that we rarely continue with, again so the chances of top pair being out there against our set when we hit it is improved. But larger pairs that win a lot of pots without improving, we want to get short handed really so we can be confident in our pair if we don't hit set. I hate four callers to my AA raise, but like it if I raise 22.