The underlying assumption seems to be that everyone uses LinkedIn/Facebook/Twitter. While it would be largely true, not everyone uses those. What would your tool say about them?
Unfortunately because we are just looking at public data online (including Github, StackOverflow, and Meetup) if people don't use those services (or contribute to open source) we won't discover them or be able to a make a prediction about their likeliness to leave.
Maybe you should start looking at Keybase [0] too. It might help you link personal websites, github, twitter, ...
Thanks! We do actually use Keybase for discovering social accounts as well.
One of the things about a small, bootstrapped operation like this is that you have to pick and choose your battles. The answer may very well be "we require data from X, Y and Z". Sure, this cuts out a lot of the market, but you don't need a ton to do ok with a small business like that.