Mods can see who gave them rep, btw. And so can the rest of staff.
We don't have it enabled for you to see because if you get negative rep (Not you, specifically) then most people would be upset that they had just received bad reputation and it can lead to flaming and just fighting in general. Obviously we staff can see who gave them rep because we're trusted enough not to go and flame the member for giving us negative rep. Some of the newer members and easily angered ones too will cause a fight though, because it's not fun to get negative rep, especially when it's not a big deal. >;
So, there you go.