Ryan Radia argues that Google won't go evil:

A major privacy breach is Google’s nightmare scenario. If anything happened to cause users to lose trust in Google, they’d go someplace else for email and search. Advertisers would follow suit, causing Google’s stock price to plummet. Google might never be able to recover from a severe privacy fiasco. Obviously, Google is well aware of its vulnerabilities on privacy, which is why Google has incredibly strong safeguards to ensure that sensitive data can’t be uncovered by a rogue product manager with an itchy trigger finger.