Exhibit A: the lottery.
Exhibit B: people who circle parking lots at walking speed looking for a convenient spot. I realize there's an end case where a lot is completely full and there's absolutely no parking nearby—and in this case, your strategy for finding a spot is probably going to depend on the layout of the lot and the distribution of times at which and directions from which people return to their cars.
But in the vast majority of cases, I see jackasses slowly rolling through multi-story parking structures waiting for someone to abandon their space. Unless you're handicapped or are carrying something heavy, this is a dumb idea.
And why is that?
Well, you'll find that if you move a little quicker, you'll be dropping the amount of time to spot an already-vacant spot, which is far more likely than happening upon someone who's just itching to throw their car into reverse...but haven't.
If you're moving near or below walking speed, odds are good that the time you'll spend walking the extra distance will be more than matched by the time you've saved by not driving like a moron.
But I always park on the 2nd level.
It's a requirement out here that at least the first three floors of your parking structure be filled at all times.