He is now actively building Disconnect, “a browser extension for Chrome and Rockmelt that disables multiple third party data tracking while browsing.” Brian explained why he left Google to do this:
I called it quits at Google three weeks ago so I could help web users better understand the data they’re unintentionally sharing and develop tools that make it simple for them to control this data (I’ve been referring to this effort as Web 2.1, a privacy patch for the web).
This is an interesting quote from him which can be interpreted two ways:
(1) He finds a lot of opportunity in privacy.
(2) He was scared by how much Google and Facebook know about you.
(3) Or Both.