having traveled all over the US and Europe, AND having been in SF for over 30 years, I find that beggars/panhandlers/homeless people here ARE more aggressive than in other places. And more numerous in the tourist areas. In other cities, there may be more scammers - people selling overpriced miniature Eiffel Towers, or more expert pickpockets - but SF definitely has most places beat for people hanging out on sidewalks asking for money.

As someone who formerly worked in social services in the Tenderloin area , I would say that SF has no idea what to do with the hordes of people who come here with no resources.