Thank you. Got distracted @ work.
As a point of interest, the story could have just been propaganda dreamed up by Caligula's enemies. However, if it were true, the most common interpretation of this event is that Caligula had no special desire to elevate his horse. Rather, he was making a mockery of everyone else. "You're a senator? You seem like a horse's ass -- just like my dear friend Incitatus!" "You're an important dignitary? Would you like to come to a feast? In my horse's stall!"
Personally, I think Obama is doing the same thing. "You stupid Americans! As an elected official I have no time to waste on you -- I tee off in 30 minutes. But do not worry, my cook shall rule over you while I am away!"