[swope]

i had a similar hand like this at a live 15/30 game at artichoke joes;

6s7s in early cutoff, raise against a bored table, call from SB.
flop is 662, no flush. i bet, SB calls.
turn is a Q. i bet, SB RR, i RR, SB calls.
river 4, i bet, SB calls, shows AQo.
i show, and he immediately starts muttering about me raising with trash etc etc.

the reason i mention this hand (yes i know its not exactly the same situation as yours), is that villain will overplay his top pair or try to get cute with Ax *often enough* to warrant a 4bet.

so i think if you bet/call a brick river, you will see an overpair often enough to justify the extra bets/risk.