A spate of violent robberies targeting marijuana businesses in the San Francisco Bay Area last month have thrown into question the survival of several small businesses, with the combined losses of those operators estimated to be at least $5 million. The crimes ranged from break-ins that resulted in minor damage to, in some instances, wild gunfights between criminals and security guards, according to media reports and sources. At least one person was shot, and a scandal has emerged over San Francisco police officers apparently looking on while burglars made off with cannabis products from a store they’d broken into. The...