> The Google-run proxy can observe the user's IP address but not the websites being visited and the third-party proxy can see the web servers being visited but

> The Google-run proxy can observe the user's IP address but not the websites being visited and the third-party proxy can see the web servers being visited but not the IP address of the visitor. Google will likely already have the user's IP from sync, safe browsing, etc, if Google's proxy doesn't know what sites are visited it doesn't sound like this increases Google's access to any user data.