[aceferret]

I think it depends on the hand...If there was no flush draw on flop, then what else could he be calling you with when there is a str8 on the board. So no flush draw on flop it's a check fold.

Now if there is a flush draw on the flop...he could be calling you with 2pair/set or the flush. When a scare card hits on river, a case can be made for a blocking bet, but i prefer to check-call or check-fold and base my decision on the villians history. Most villians will just check if they were drawing for a boat and missed. Only a select few will pot the river(especially at the lower levels) when a scare card hits that does not help their hand.

An interesting aside to this post. How many of you pot the river when it's checked to you because a scare hits that does not help your hand. I believe it is very profitable to do so when the three flush hits that misses both of you.