I personally think, that for one thing, people shouldn't give reps for things unrelated to the forums, and to helping on the forums. For example, "for being a girl" or "for being hot" or "you're a really great person on IRC" aren't really good reasons, as they don't relate to how a person is on the forum.
I know that us girls do tend to get more votes than others, I would like to hope that all of my reps are un-related to being a girl though. I know that there is at least one girl on here, (who hasnt posted in a while), who never posted her picture, and has quite a low rep, when she did help a lot. So I dunno.. maybe for the girls getting reps thing, it's somehow related to the posting of our pictures. Or maybe i'm just being completely off the mark, and am thinking on things way too much.
Imho, I think reputation bans would be a good idea. Say, depending on the amount of rubbish reps you give, after a certain amount, it bans you from giving any reputations at all, for a set period. If you persist after this, then a 24 hour ban, as someone else suggested.
I think reputation moderators wouldn't be such a good idea, although it could work. I think it wouldn't work because it would be hard to select people who can fairly judge what is a good, and what is a bad reputation. It would also have to be elite members, tbh, who were the reputation moderators, as they, imo, are more trusted than any of the normal members. And normal members could also become biased towards their friends. But as I said, it could work.
A reporting system for reputations could easily be abused, as you could simply report a reputation you don't like, and it might not be removed, but it would waste admins/moderators time, because they would have had to read through all the reps, and it would be pointless to come to a lot of reps that shouldn't have been reported in the first place. Also, you could get members who report peoples reps, just because they don't like that person.
As for increasing the amount of posts that you have to have to give a rep.. Well, that would also increase spam, as people would be desperate to get to that certain number. And also, it is not fair on certain respected forum members, who don't post as much as others, and don't reach high numbers for quite a while, to not be able to rate fellow members for their good help, etc.
I have seen on some forums that also have a type of rep system, that you cannot give a reputation to a member that doesn't have a certain amount of posts, or hasn't posted yet. I think that could also be a good idea. For example, you'd have to have above, say, 10 posts, before someone get give you a reputation. This would stop people who are new, and are known from IRC, or something, getting reps suddenly, and it would give us all a chance to have something to view, to base our reputation for that user on.
Just what I think. Thanks for reading it, if you do.