Circumstances of Thiel's departure from Y Combinator remain murky, but it appears he left last year. : Polarizing billionaire venture capitalist and PayPal co-founder Peter Thiel is no longer a partner at Silicon Valley startup accelerator Y Combinator. Sam Altman, the accelerator’s president, made a very low-profile announcement of Thiel’s departure, adding “Peter Thiel is no longer affiliated with Y Combinator” to the top of a 2010 Y Combinator blog post welcoming Thiel as a part-time partner. Thiel, a libertarian Trump supporter, had sparked controversy when he joined Y Combinator, which is probably the best-known startup incubator in Silicon Valley.