When the NBA enacted its anti-flopping rule structure prior to the start of the 2012-13, they did so by laying out a series of fines for players who perform "any physical act that appears to have been intended to cause the referees to call a foul on another player" (via NBA.com).
The official league press release went on to say that flopping will be determined by "whether his physical reaction to contact with another player is inconsistent with what would reasonably be expected given the force or direction of contact."
Any time that a punishment will be determined based on reasonable expectations, there is clearly going to be some gray area. What's reasonable to one official won't necessarily be considered reasonable to the next.
Flopping has no place in the NBA, even if we're unable to define what exactly it entails. Players know when there's a flop because they feel the amount of pressure applied. Fans and analysts can judge flops with the helpful hand of instant replays.
But for referees calling the game in live action, flopping is tough to determine. And it's immensely more difficult considering the vague direction they've been given.
Contrary to an overgeneralized, out-of-touch belief, flopping is not confined to European players. In fact, it's a wide-spread plague affecting the global game:
Drew Gordon's flop against Lietuvos Rytas. Deserved a technical foul. Just disgusting... but also funny. bit.ly/TwRoLC— LithuaniaBasket (@LithuaniaBasket) November 30, 2012
Despite the relative quiet on the punishment front, the problem is just as rampant now as its ever been. And there are a few NBA teams who've been quite active with "reasonable" deceptions.