There are two plays:
1) Raise. The reasoning behind this decision is simple. You figure that there's a good probability that villain has overs (missed paint) and you can take the pot away from him by showing strength. You price him out of his overcard draw immediately, or else receive the bad news.

2) Call, with the intention of stealing the pot if checked to. This play is the same as the first, with an imporant distinction. Calling gives you information at the cost of a potentially harmful free card. To second barrel on the turn with missed overs (after a call) is risker than c-betting a flop. It takes balls. Thus, a villain wih missed overs is checking the turn frequently. If he checks, you can probably easily take the pot away (now confident that villain has dogshit). If villain fires, you know you're beat. The only difference is that your opponent might catch a needed ace / paint card on the turn.

Each move is justifiable, and depends on the opponent. Like the above poster stated, if the villain is fearless wih marginal hands (and will continue to bet a small pair / ace high), then calling the flop sucks. Whereas a flop raise might've scared him off, your call means nothing to him and a turn bet will put you in a tough spot. Against the more common (passive) opponent, calling is much better. Getting his small pair / ace high (marginal hands) called will frighten him and he'll check the turn waiting to give the pot away.

As far as the last point made, that raising may be greater +EV in getting better hands t fold, I disagree. Both plays are trying to get better hands to fold. The calling play is merely trying to bide time (and get more info) before pulling the trigger. Unfortunately the next card might screw us. Against a weaker player I call; calling can catch air just as well (the overs are missing the turn often enough anyway), without the downside of losing a few bets more to an overpair / unlikely trips.

Against a no-BS "i'm betting the turn b/c you weakly called me" player I'll let him know "i have it" by making it 3-4x to go on the flop.