Not betting enough for value.
It goes in peaks and troughs, when players bet more on the turn or river. I see that players overbet pots a lot more than they used to. Having a pot of $75 and then betting $200 into it, to force your opponent to fold, seems a common occurrence. I would not play like this, but some do, and if it picks up being done, then the chance for players like me to bet $25 into a $75 pot, will happen more often, and catch the opponent out.