It’s called Mission Mattress. And it’s not just doing updates about itself; it also covers such other Mission favorites as cannibal pigeons, shoe piles — and Occupy Oakland.
(Thanks, Cristina!)
UPDATE: There’s a Flickr group covering similar territory.
Damn, I wish I’d thought of that! Maybe a Tumblr page called “Mission Pee-Stained Sofa Cushion”?