From Army Field Manual 7-21.13, The Soldier's Guide:
4-7. The salute is not simply an honor exchanged. It is a privileged gesture of respect and trust among soldiers. Remember the salute is not only prescribed by regulation but is also recognition of each other's commitment, abilities, and professionalism.
In a way we shouldn't be surprised. After living through the dark years of the Clinton regime and thinking that we had reached the nadir of disgrace with the Beverly freakin Hillbillies in the White House we have had the current crop of low-bred grifters imposed upon us who have actually managed Bill and Hillary Clinton look cultured and accomplished.
The President isn't required to render a hand salute, since Reagan, though, it has become customary. This salute by Obama may serve as a useful metaphor for his entire administration: sloppy, ill thought out, inappropriate, callous, selfish, and disrespectful. Though, in his defense, he may have been running from that thing covered in a red bag that seems to be pursuing him down the stairs.