I only got 500 karma quite recently myself, though getting from 500 to 750 took no time at all. I think you could get karma pretty quickly if you really try har

I only got 500 karma quite recently myself, though getting from 500 to 750 took no time at all. I think you could get karma pretty quickly if you really try hard for it by trying to get to posts as early as possible and saying the obvious thing that everyone is thinking, but I don't think you could really scale this up to a meaningful number of accounts. I don't think you could really do much damage, also because posts themselves (as opposed to comments) can't be downvoted (unless that's behind some other karma milestone I can't reach yet).