I have to say it is rather jarring to see homeless people in SF living in tents and cardboard boxes on streets lined with skyscrapers and around pristine parks and plazas.
So while the city does have a ritzy tech feel in the right parts, it is disconcerting to know that amidst so much concentrated wealth there are a lot more homeless people than you would expect. Really, a lot.
Unfortunately it's not as if these are all down-on-their-luck folks in between attempts at The American Dream. A lot of homeless people - in SF and in general - have mental illnesses and addiction problems and they do need help.