Do you connect your Facebook or Twitter accounts to apps or free services you've forgotten about or don't use any more? Lots of free services offer the option to use your existing social media accounts to register, that look like this one:

Here's what Nick Bilton says in the NYT Bits Blog:
Whether you realize it or not, dozens — if not hundreds — of apps and services have access to your social accounts and can see everything you’re doing online. Tweets, Likes, your location, are all there for the taking. What’s worse, there’s a pretty good chance you unwittingly gave them permission.
I noticed that hundreds of old apps have access to my Twitter, Facebook, Google and LinkedIn accounts.
It was time to do a little cleanup.
Just like the spring cleaning rule that says, “If you haven’t worn it in six months, throw it out,” you should use the same edict with your online data: “If you haven’t logged in to an app or site in six months, revoke its access.”