When I'm introducing SE to family and friends and they ask me if it's safe to login to StackExchange using their Gmail id, I don't have an answer to give them.
How is it safe? How can I convince anyone that their Gmail password won't be compromised?
How does the login work behind the scenes?
p.s: I first logged into SO by creating an OpenID because I couldn't convince myself that a Gmail login would be safe.