The numbers cited by Campos and others -- 45 fires in two years -- also weren't necessarily as suspicious as they seemed. It turns out that 25 fires a year is about average for the Mission. But there's a reason that arson is on everyone's mind: While the number of fires has stayed steady, the value of the real estate in question has not. The 27 fires that burned in the Mission in 2006 caused $2.6 million in damage; the 22 fires in 2015 caused almost $15.6 million in damage.
I later spoke with the former head of the San Francisco Fire Department's Arson Task Force, John Darmanin. He told me he didn't know of any cases of arson explicitly tied to landlords wanting to get rich from gentrification but that the arson department was so overloaded and under-resourced that cases "do not get the level of professionalism and investigation that they deserve." There were fires, he said, that "very well could have been arson, but we just didn't have the manpower to devote to those cases."
Here's a profile of a landlord who went to jail for trying to hire someone to burn down his apartment building.