Did Letterman tap Keri's ass too?

Keri Hilson performs her great song, “Knock You Down” live…and it sucks:

Jeez, her voice doesn’t sound like a voice that could naturally hit any of those notes she did in the song. She really ruined the song for me now. And what’s good with Kanye poppin her booty? First Wayne then Kanye? Is her M.O. gonna be any guy that performs with her is allowed to tap that ass? Hmmm, interestin rep she’s building. And she needs to grow her fuckin hair out!