Just ran into something interesting - not sure if this is a Known Issue or not. Using Safari 5.0.5 on OSX 10.6.8, I was authenticated into a Google property (gmail). Switched to "Private Mode" in Safari, then attempted to log out of gmail and switch to a different account. Even after clicking on "Sign in as a different user" I am still returned to the same page, prompting me to authenticate the last user logged in.read more
