The article goes into it from a historical perspective, but one only has to search "SFPD Corruption" to find many examples. And officers who try to be ethical get punished by the others.
As I noted, the SFPD is 50+ times the size, and I'm interested in an actual metric, not anecdotes. I'm pretty suspicious of the contention that a private police force would be somehow immune to corruption - it certainly hasn't been the case with groups like Blackwater.
http://www.sfweekly.com/sanfrancisco/sfpd-tries-to-fire-cop-...