Using the Google+ news to make a point about attack surface: Your old online accounts can put you at risk even if you’re not using them anymore.
Laughing at Google+ bug? You’re making a big mistake.
The popularity of Google+ is a distraction when you’re thinking about Google+ as part of a consumer’s broader “attack surface”…The more accounts you have, the bigger your digital footprint and the wider your attack surface.
Taking it a bit further:
Does the account still have access to anything else? Unlink it!
Do you use the same password anywhere else? Change those passwords!
Does it have private information on it that could be used to impersonate you on another account? Think about whether you still want to keep it around.