Jill Sobule is, like, so yesterday...
Seriously, great song (thr Jill Sobule one), I think I saw it because of GA a few months back. This site is ripe with people willing to lead the poor innocent me astray.
As for Kate Perry, she's got a hit, and that's a hit, plain and simple. A catchy chorus, which actually starts the song, basic and efficient rhythm and chords, great lyrics, mixing lust and guilt, how can you actually get it wrong for a judeo-christian audience raised on R n' R?