The worst levels of homelessness I ever saw in the states was in San Francisco. There would be somebody panhandling on each of the four corners of every intersection you crossed. Apparently a lot of it is to do with the climate. Homeless people travel to San Francisco (especially during the winter) as it is safer to sleep rough in, less change of dying of exposure.
The tech industry is also having an effect as all the money is pushing up rents drastically and resulting in people being pushed out of where they live. Those on the bottom of the housing ladder just lose their homes/rented accommodation.