I shot this on Bush Street in San Francisco. I have no idea what it is, but I will do some research and post an update.
UPDATE 2-24-2012: I found the following information using an image search:
“Parasites are rarely adorable, but this tiny little cabin in San Francisco certainly is.
The structure, which measures approximately W7 x D8 x H11 feet, takes on a 19th-century architectural style. Constructed from vintage building materials – it has a welded aluminum frame, with an exterior finished with 100 year-old reclaimed barn board from Ohio – the dwelling is meant to be an homage to the romantic spirit of the western myth and a commentary on the arrogance of westward expansion.
Sure it might not be lived in, but it does seem to be functional and could actually become someone’s home at some point.”