From Slate:

Their Fates Were SEALed

Forget the U.S. version of the Bin Laden raid. Any adult male found in the compound was a dead man. By William Saletan

You can also look at it the other way around: the SEALs did a fine job of not hurting any of the large number of children in the compound and not hurting any neighbors, and killed only one woman and shot another one in the leg or foot. Meanwhile, all adult men in bin Laden's compound were, by the fact of their presence in bin Laden's compound, assumed to be sworn enemies of the United States and therefore terminated with extreme prejudice. Compare it to the NATO aerial attack on Tripoli the night before that managed to kill a couple of Col. Cathaphee's small grandchildren without getting the target. The latest news from Obama Administration sources (from the Washington Post):

U.S. officials provided new details on bin Laden's final moments, saying the al-Qaeda leader was first spotted by U.S. forces in the doorway of his room on the compound's third floor. Bin Laden then turned and retreated into the room before being shot twice - in the head and in the chest.

"He was retreating," a move that was regarded as resistance, a U.S. official briefed on the operation said. "You don't know why he's retreating, what he's doing when he goes back in there. Is he getting a weapon? Does he have a [suicide] vest?"

It sounds like they shot him in the back. In the Wild West, that was supposedly considered unsporting. I recall asking my cousin around 1966 about the plot of some cowboy show episode (Gunsmoke? The Rifle Man?) that turned on whether or not a reward would be paid for a desperado wanted dead or alive who, it turns out, was shot in the back. Saloon sentiment in the show was against paying. (As a rather pragmatic and bloodthirsty seven-year-old, shooting bad guys in the back sounded fine to me.) I don't know what feelings are like in the Wild East.

This could explain dumping bin Laden's body into the sea.