[PokerFink]

Thanks for the replies everyone.

My immediate reaction was the same thing DJ Sensei and some others have said - he's not really representing anything, so if I'm going to value bet, I probably have to call the raise. I called very quickly without much thought and got showed 44 for a boat.

In hindsight, while I still feel his line doesn't represent a big hand, there aren't a whole lot of hands he gets to the river with that he thinks "omg I have to bluff now." If he has a mid pair, he's calling or folding, not bluff raising. The vast majority of players in the game aren't tricky enough to bluff c/r the river, so I think I can safely fold this in the future.