@38: Enough with the bridge jokes! Last time someone said that, London Bridge ended up in Arizona.

It seems to happen all the time at LAX (I fly in and out of there, the Southwest terminal, about once a week). Generally, it's considerably faster than 1/2 hour, though, at most a minute or two.
I always assumed it was yet another Totally Silly Absurdity, something they do To Seem Acceptable.