Found in the Thursday, May 27 calendar datebook section of the San Francisco Chronicle.
"Masterbate-a-Thon Center for Sex & Culture Executive Director Dr. Carol Queen will be joined by various celebrity hosts as competitors vie to beat the current world time record. Benefits the CSC. Sunday. Competitors arrive at 10am, non-competing masturbators at 2pm and audience may arrive after 4pm. $25 (voyeur seating). Mission Street, San Francisco."
And what are you doing this Memorial Day weekend? Besides steering clear of Mission Street, that is.