User Reputation...

[Robbie Robb]

Well, I think that if you're leaving postive rep, being known isn't a bad thing. However, if leaving neg. rep, being known could lead to a huge PM (or worse, public) flame war or retribution unless the neg. rep has a comment that is constructive on why it was negative. Even then...

While I admit, it's nice to see who was kind enough to give me rep points, I think that the possible downside outweighs any benefits to seeing who gave you rep.