In a way, Sam Altman is back where he started. The Y Combinator graduate will take over from co-founder Paul Graham as the head of the prestigious Silicon Valley accelerator.

Altman's company Loopt, which provides location-based services for smartphones, started with a seed investment from Y Combinator in 2005, its first batch of startups. Altman was a freshman at Stanford. He took to the stage at the Apple Worldwide Developers Conference in 2008 with one of the first apps in the new unveiled Apple App Store (here's a video of a very fresh-faced Altman).

Image: Sam Altman, the new president of Y Combinator. twitter.com/sama