= Excellent Reporter (1000 Good Reports) 
= Bad Reporter (200 Bad Reports) @theymos, while you're at it, can you reduce the time requirement between reports?
Both star will show if a person have (for example) 300 Good Reports (1 star) and 100 Bad reports (1 star).But how about if.
if GoodReports >= BadReports then Good Report Stars will be shown.
else
Bad Report Stars will be shown.
Edit.
These two guy's reply below were right. I think it is much better to exclude Bad report Stars in my suggestion. By the way it's just an option.
By looking and having these shiny stars on their profile, members will be encourage to help reporting.
However, I also like BTCforJoe's suggestion.