Weak or not Weak?

[SirFWALGMan]

I think checking the river applies even more so in NL. I had position on a guy with AA. I 3x pre-flop and like 4 people are in. The flop is K3x, so I throw out a bet. The next card is a low card. He bets, I call. The river makes a possible flush, he checks. I think I am beat, and I am pretty sure he is not going to fold if I put a big bet in. So I check. It turns out he had K3 and flopped two pair on me. Oh well. What can you do about that? So TPTK is definatly a good check on the river in NL I would think.. unless you are pure bluffing..