I second the mentioning and advocating of this feature. For my main Chrome user, I have StayFocusd installed, and its workings make themselves known in various debug outputs, so I switch to a stub user setup on Chrome when doing dev work. I also switch the theme so that I subconsciously associate the non-logged-in, green-colored browser with "hey, it's work time". On a separate user instance, I'm logged into Facebook but have otherwise thrown away the password...it's amazing how the friction of a simple clicks (it only takes a right-click to pop-open the available Chrome users, then left-click to select one) can almost by itself break the reflexive whim to check social media accounts.