I think people here got the idea that SF is post-apocalyptic by visiting it for conferences, since the area around Moscone is especially bad, you only have to go on a short wander for lunch before you end up in the Tenderloin, etc.

The last time I visited SF (for WWDC), I witnessed more crime first-hand in one week than I had in my entire life before (and since). I also witnessed more homelessness than I've seen in any single city.