Airbnb has a reputation as a scofflaw. They've also contributed to the insane rental prices of the city, as they've taken many units out of the housing market.
"Airbnb hosts have faced some unpleasant surprises, including eviction notices and city citations. San Francisco landlords are increasingly using Airbnb hosting as grounds to evict tenants in rent-controlled apartments that could rent for higher amounts. The city Planning Department has warned hosts they could be subject to fines of $250 a day unless they stop renting out their apartments, which removes scarce rental housing from the market."
http://www.sfgate.com/business/article/Airbnb-issues-strong-reminder-to-hosts-to-obey-5393565.php