Also, since people are arguing about why IKAG and Dark Horse are risks, I'll explain why they aren't:
IKAG-
1. Katy was NOT an established artist. She had, legitimately, nothing to lose. This does bad? She's no worse off and can try again with a new sound. It does well? She becomes a huge star. That's not a risk, she's losing nothing by doing this.
2. Lesbianism/bicurious were not exactly unheard of or insanely controversial at this point, especially just girls kissing
3. The song isn't actually about either of the above anyways. It's a straight girl kissing another girl cause she's drunk and straight dudes think lesbos = hot.
4. She doesn't even kiss a girl in the music video when the song is about it

JUST because she's worried it might hurt performance or stop it from airing on MTV or something
Dark Horse
1. Super popular and voted promo single
2. Was already doing well when made official single. Guaranteed hit