I made the mistake of taking the 19-Polk to my afternoon destination this past Saturday & so got a front-row seat for SantaCon, the modern revival of the yuletide tradition of misrule that once got Christmas banned in this country. Young people in Santa outfits, or simply in red apparel, prowled the sidewalks & lined up at bars all along Polk Street from Union Street to Geary. I saw a team of Santas pulling a large wooden sleigh with female riders down the street. A posse of wassailers rode the bus with us for several blocks. They were buzzed but well-behaved.
I rode BART to the East Bay in the evening, & there were Santas in every car, in various degrees of booziness. The official San Francisco SantaCon Web page clearly states "This is not a bar crawl" then lists about 50 participating clubs & bars.