I do not think Def Jam signing Amerie has anything to do with Rihanna....It's called Def Jam trying to be smart. Rihanna has been working non-stop by dropping 3 albums back to back so she definitely will not be dropping another album next year. Amerie, on the other hand, is eager to have another US release so Def Jam is a good way to go and she would not be competing with Rihanna when her album drops.