This story reviews the sordid history of San Francisco’s attempts to use surveillance cameras for crime prevention and prosecution. Other cities, like Chicago, are said to have deployed a much more successful camera infrastructure. It also touches on the existing shot-spotter infrastructure in San Fracnscisco:
http://hoodline.com/2014/10/lights-cameras-inaction-san-francisco-s-broken-surveillance-state
As an interesting coincidence, PG&E announced significant reductions in the fees charged to install shotspotter detection devices:
Castro Patrol encourages residents and businesses to install cameras wherever possible as they are increasingly being relied upon to solve crimes.