[RobNottsUk]

Well my opponents are frequently calling on the flop with bottom pair even. Suppose they had an Ace, with a T or a K, they'll call on a gutshot on the turn. But someone would also call on a flush draw, picked up after calling loosely with a 6.

So that player, is going to call you on the river with trip 6's, despite the str8 being obvious. But they wouldn't bet that hand, so you really have to think about what those players would do, and whether they go for check/raise if they fill up on the river etc.