Of course five games isn't enough.
Or wait, maybe it's too much.
The math here is really easy. If Hamels serves his suspension during a five-game stretch in which the Phillies have a day off, Hamels won't really miss even a single start.
This current stretch, for example. Hamels pitched Sunday, the 6th. The Phillies have Thursday off. Hamels' would normally pitch Saturday, with five days rest. Instead he will serve his suspension and pitch Sunday, with six days rest; meanwhile, Roy Halladay starts Monday night against the Mets, and can pitch again Saturday on his usual four days rest, which he might actually prefer.
So Hamels might be slightly inconvenienced, waiting an extra day to pitch and thus falling out of his routine. Pitchers love their routines. But Halladay gets to stick to his routine. If you project all the way through the end of the season, and assume a) the Phillies will need to win every game, b) neither Halladay nor Hamels ever get hurt, and c) Halladay is better than Hamels -- and those first two assumptions are pretty shaky -- the Phillies actually benefit from this suspension, because Halladay might actually have gained a start while Hamels might lose one.
Then again, nobody wants to be suspended. It's a hassle. There might be some slight deterrence with a five-game suspension for a starting pitcher ... but if so, it's oh so slight.
If you're really looking for deterrence, you would have to suspend Hamels for nine games. In this case, if Hamels were suspended for nine games, in that ninth game the Phillies would have to either start Halladay on short rest or call upon someone they truly don't want starting: a reliever, or someone from the minors. That would be a deterrent, because then the suspendee would actually feel like he had let his team down.
There's a problem here, though ... Suspensions are built on precedent. I doubt if a pitcher has been suspended for nine games for throwing at a hitter. Which means if Hamels appealed his nine-game suspension, he would probably win and we're right back where we started.
So what's the point of it all? Major League Baseball has to do something. Sure, it's only a slap on the wrist, but you must remember that most of what Major League Baseball does, when these things come up, is designed for public-relations purposes. They couldn't do nothing. That would have looked bad. So they did something slightly more than nothing. Which is better than nothing.