The first couple of movies, you can't blame them. They don't know that someone's sneaking around killing people. Toward the end of the original series, well, you'd think the mass murders every summer would have convinced them to move years ago. Mind you, it could be that the smarter ones actually did move away, and we just get to see some of the people who couldn't put two and two together getting killed. So, yeah, at least some of them were just too dumb to live.
You can't blame them for any of the movies, really. The first one was a crazy woman taking revenge decades after her son's drowning, nobody would have expected that.
Part 2 and 3 take place on consecutive days, so nobody from Part 3 would have heard about the killings that happened in part 2. And neither of them takes place at Camp Crystal Lake (at least not the original one).
Part 4 takes place the day after Part 3, and Jason supposedly died in part 3, so nobody in Part 4 would have had reason to suspect him to still be on the loose.
Part 5 is an unrelated string of murders by yet another grieving parent, years after Jason died (and was cremated). It doesn't take place anywhere near Crystal Lake.
Part 6 is back in Crystal Lake, but Jason's been dead for several years. NOBODY could have forseen him being resurrected by a lightning strike (especially after he was cremated ... uh, just never you mind about that).
I don't think anybody is at fault for not expecting a psychic girl to bring him back to life for Part 7. That doesn't excuse the authorities for not retrieving his corpse from the lake in however long it was since Part 6, though ...
Part 8 takes place far away from Crystal Lake (yet AGAIN after Jason's been dead for a while), so nobody would have been expecting that.
Part 9 ... let's just not talk about that.
The scientists keeping Jason for study in Jason X may have had it coming, but the kids on the spaceship hundreds of years in the future sure can't be blamed for not expecting him to come back to life.
And in Freddy vs. Jason he was once again well outside his normal stomping grounds and had been dead for a long time before the movie started.