My battery currently hold 6565mAh. I don't believe it's right because when I ran Snow Leopard it was a solid 7.5-8 hours of usage like they advertise.
Lion tends to be more resource hungry then SL.
I don't know whether twitter.app is resource hungry, but ~ 15W when idle sounds like a bit too much for a long battery duration.
I stopped using the twitter app because my battery life seemed to dramatically decrease when I was using it.