Baseball-intellect.com (a site whose writer is a big fan of Paul Nyman) wrote a bit about Homer Bailey and his mechanics, stating that he liked his scap load and elbow rotation into release (both of which he claimed were better in 2006). Well, the reason that he isn't getting better "scap load" in 2008 could have a lot to do with the fact that it is inherently injurious and it leads to damaged shoulders, so as a result, he's not doing it because he already feels a lot of pain from his mechanics.
Nevertheless, the image above shows that Homer Bailey clings to the only way he knows how to throw a baseball, which involves reverse rotating the shoulders, extreme early pronation, and a severely forced horizontal abduction of the shoulder.
Tempo: Bailey is 21 frames from maximal leg lift to footplant. Average to Below Average.
Arm Action: Horrible. Not only do Homer Bailey's shoulders begin to turn while the ball is below the shoulder line, but he has a forced scapular loading pattern caused by arm drag and he exhibits signs of early pronation. I expect Homer Bailey to experience both shoulder and elbow surgery in the future (but I would bet on shoulder surgery first). Extremely Bad.
Ball Release: Also pretty bad, since he is actively supinating through release to throw his curveball and cut fastball. At least he sticks his pitching arm shoulder into the target reasonably well. Bad.
Followthrough: This is also really bad since he has a lazy glove arm, and instead of continuing his momentum forward, he pivots on his stride leg (watch the full video). Bad.
Homer Bailey is a textbook example of how not to throw a baseball, right up there with Anthony Reyes, B.J. Ryan, and Mark Prior.