I think in general if you're going to raise some low-talent limpers in a cash game, you should have a real hand or a better sense of when to give up. I'm always suspicious when the action goes like this: limp, limp, I raise big, call, call. Then one of the limp-callers donks into me on the flop; even though it's a weak bet, what about this situation is screaming "raise $3, he's definitely going to fold"?
I'm a habitual blind stealer and run into action like this all the time. I agree with Andy here. Weak bets post flop after limping generally mean weak hands at the lower levels. I'd say maybe 20% of the time you're up against a set or whatever, but it's usually pretty easy to tell and pretty easy to pitch whatever crap you have. If I raise on the button PF with a marginal hand and some limp/caller bets 1/4 pot into me, they're usually getting a big reraise back--they have to be convincing if they want me to drop my T9o.