[kstenerud]

1. The weather in San Francisco is nice (so you won't freeze to death).

2. The laws are friendlier towards homeless people.

3. San Francisco is liberal, so the people will be friendlier on average to the homeless.

4. America's public transport systems are terrible, but you can go quite a distance on BART and the city buses and it's easy enough to ride for free.

5. If you're stuck begging in order to live, better to beg from rich people.

If you're homeless in America, it doesn't get much better than this.

[armitron]

Most importantly, you forgot the wide availability of hard drugs.

Downtown SF is an open drug bazaar, probably the biggest in the USA if not the world. Police do not go after the sellers and the city has for years maintained and enabled this nonsensical anything-goes policy.