I did a little video a while back about how that whole logging in with a third party app works (3-Legged Oauth -- A Love Story). What I didn't talk about is how many people use things like Facebook to log into OTHER things, which is exactly what we use OAuth for.
You can also use Twitter or Google to log into websites and apps. But how many people use these different services as a away to log into ANOTHER service?
Well, the folks at Gigya did a bit of research and this is what they came up with. Facebook by far helps more people log into some other service or app more than anyone else, which is cool because it's only one password, but kinda scary if you're worried about Facebook knowing too much about you, because this just expands their footprint a little further than where you post pictures of cats jumping into boxes...
Here's the infographic. Click on it for full size:
Logging into Myspace in 2014