Steam, we need to have a talk about your achievement system...

Oh damn. That seems a bit over ambitious :O

Looks like I even own most of the game on top of that list. Good reference to have to remind oneself to try to avoid to even start them up :)
Zen VS Zombies looks kind of interesting though

But you have to actually do something to get them

So?
But does that mean other should also have that much achievements. I think TF2 doesn't have unreasonable or nuisance achievements, I looked at some achievements thought I haven't played a game. It is justifiable in a sense because it has achievement based on various characters, skills, tasks and game-play.
So should a normal HOP game should contain 520 achievements, I don't think so, unless they give us variety of 'sensible' tasks that can be done within a game.

If the achievement are justifiable or sensible in terms of gaining it, yeah they can put. But mere quantity doesn't sound good to me. Most of them just do like for example jump 5 times, jump 10 times , jump 15 times..... jump 100 times. Multiple achievement for a same task. Task like those are just monotonous, its not a good achievement.
And comparing to other games doesn't help at all, TF2 being more versatile in-terms of game-play, skills and tasks, there might be various justified achievements, but taking that game as an account for hundreds of achievements for a mere 5-10 hr game is really a bad practice.

neither people who want +1s