Y Combinator has added four new part-time partners, one new full-time partner, and a full-time partner is reducing his role to part-time.  That’s all according to a post on the official Y Combinator blog at Posthaven.  Three of these new advisors have previously founded YC-funded startups.  One of the new advisors is the first YC partner with direct experience taking a company through an initial public offering.

YC alumni joining Y Combinator include Kevin Hale of Wufoo (YC W06), Michael Seibel of Socialcam (YC W12), and Steve Huffman of both Hipmunk (YC S10) and Reddit (YC S05).  Mr. Hale will be joining as a full-time partner.  Mr. Seibel and Mr. Huffman will both be part-time advisors.  All of these new people have direct experience with reaching an exit: Wufoo was acquired by SurveyMonkey, Socialcam acquired by Autodesk, and Reddit purchased by Conde Nast.

Dalton Caldwell and Andrew Mason are also joining YC as part-time advisors.  Mr. Caldwell previously co-founded both App.net and imeem, which was purchased in 2009 by MySpace.  Andrew Mason is the co-founder and former CEO of Groupon.  Mr. Mason is a very unique addition to Y Combinator.  Up until now, Y Combinator’s partners have only had liquidity experience through acquisition by another company.  Andrew Mason brings the experience of having successfully guided Groupon from inception all the way to an I.P.O. on a major stock exchange (NASDAQ: GRPN).  It will be interesting to follow the start-ups advised by Mr. Mason and the direction they take in growing their business.

Harj Taggar is reducing his role at Y Combinator to advise only part-time.  Mr. Taggar originally founded YC W07‘s Auctomatic with Patrick Collison, who later started Stripe.  Auctomatic was acquired by Live Current Media in 2008.  Harj Taggar subsequently joined Y Combinator as its first new full-time partner after the founding four (Paul Graham, Jessica Livingston, Robert T. Morris, and Trevor Blackwell).  According to the announcement, Harj intends to travel for awhile and then work on a new start-up.

As somebody who keeps track of such things, Y Combinator now has ten full-time partners and eight part-time partners.