I've heard estimates from 5,000 to 15,000 people. I'd guess it was somewhere in between. We marched through the financial district and then gathered at City Hall.
Images from Occupy SF march on Oct. 15th
Day: October 16, 2011
"The safest general characterization of the European philosophical tradition is that it consists of a series of footnotes to Plato." —Alfred North Whitehead
Footnotes2Plato 