The idea behind flopping is to (a) create a foul out of nothing, (b) turn a borderline foul into a called foul, or (c) make sure an actual foul is called. The first should be fined or otherwise penalized, it's cheating. The third is fine with me, sometimes you need to call attention to a foul.

The middle one is difficult to regulate. On the one hand, I wish players would play through more borderline calls. On the other hand, I can see why they try to turn them into fouls, and there's enough there that it's hard to fine or penalize them for it.