I think it's worth pointing out that Justin.tv led to the two largest YC exits to date, Twitch (Justin.tv pivot), and Cruise (founded by Justin.tv cofounder Kyle Vogt and Justin's brother Dan).
In 2008, Justin.tv co-founder Michael Seibel found Brian Chesky crashed on the floor of a hotel in Austin, offered him space in his room, began coaching him on how to build a startup, introduced him to the rest of the Justin.tv team, and ultimately brought them into YC! (and look where he is now: https://www.youtube.com/watch?v=hP6TH3pBPi8)
I look forward to more of the same :)