Yeah, it's now beyond odd, the empty seats have now prompted an investigation. A writer from the WSJ offered this hypotheses:
How did that happen? Blame a mix of prime tickets that go unused by corporate sponsors, international sports federations and rights holders. Adding to the unfortunate visuals: Bored media stayed away in droves for preliminary competitions in some sports. This is a common Olympics phenomenon, especially early in the Games when medals aren't yet on the line.
The last part is a tad iffy, since even the final heat of the Lochte-Phelps showdown in the 400 IM did not appear to draw a packed house. Plenty of photogs, sure. But still not jammed with spectators.
It also sounds like blocks of tickets were allocated to participating nations, for their fans and even athletes. But it's still a major clusterf**k. My friends who are over there, one of whom is a US swimmer's coach's wife (holy degrees of separation) , goes on a daily quest to round up tickets for that day's competition.
The LOCOG better figure this out soon, both from a revenue standpoint and a PR standpoint.