SF is known to be a very permissive city. Certain squatters have taken to sunbathing in the nude (even in winter) to the delight of tourists.
UPDATE: As of February 1st, 2013 public nudity is no longer legal in San Francisco. Comments from sunbathers are vague, at best:
A few California sea lions began "hauling out" in PIER 39's West Marina shortly after the 1989 San Francisco Loma Prieta earthquake. The boisterous barking pinnipeds started arriving in droves and took over K-Dock in January 1990. At first they numbered from 10-50, but due to a plentiful herring supply, the available dock space and protective environment, the population soon grew to more than 300 in a couple months.
For the past two decades, The Marine Mammal Center, an organization devoted to the rescue and rehabilitation of marine mammals, as well as to the study of these animals' health, advised PIER 39 that the sea lions should be allowed to stay.
