I've called a few more of these monkey bluffs than I like at the $100 game lately with AK or JJ to a scary but A free board. Invariably it is a Swede with a gutshot or a even more invisible running draw in my raised pot after my continuation bet, I'm running good against this aggression either way.
Maybe 2/3 pot isn't enough, or they assume I raise QJ and A3 is good, or that I'm overly weak tight and can't call that bet with out the stones. I have no real clue as to what Scandanavian poker players are thinking when I stack them by four times and they play into my raise, but it must be, "He didn't come here to gamble, I did!". Maybe my username is listed as a soft spot on an European poker forum, but it has happened enough to me lately to note it.
The same type of person enjoys making weak hands like small pairs and suited connectors 7x the blind but under-raising/betting very strong hands, I think the key to recognizing this as a bluff is an opponent that normally plays for value goes ape with all in. Since they normally would wait for the turn or make a reasonable raise the all-in is a steal. This would be a bad LAG that isn't playing his good hands fast enough and making calling with either 6 outs or having to dodge 3 outs a better than even money proposition.
I see some of these monkeys that are on the verge of being very good LAGs once they learn to use folding in someone else's raised pot with out a hand technique and play the good hands the same as the bad. I think the majority of them will go broke fast and it isn't from a lack of action 7x raises.