I think the forums site-reference.com use a nice system than this retarded RepRank thingy.
I just picked up a thread as an example so you can have a look:
SEO at your fingertips
If you look beneath the users Avatars, there are some little buttons, like "Thank you", "Buy me a coffee" or "Buy me a Beer", etc.
As a member there I use them already. The "Thank you" button is used if some one was thankful for your tip. But there is no way to rate someone negatively. The other buttons are linking to your pPaypal account when a user would like to donate for your help. And all that is up to you if you want to use them at all.
I think it is a very interesting, encouraging and fair system.
What do you all think about that?