IMHO (based on my reading, and based on my observations of a certain organization where I went to college), the distinguishing feature of a cult is the exploitation of unanimous peer pressure (cf. the Asch conformity experiment) to make everyone follow one charismatic dictator.
E.g. you give all your money to The Guru because that's what a loyal follower of The Guru does, and all the people you hang out with are loyal followers of The Guru. All the people you hang out with are loyal followers of The Guru because they love you so much and they have so many things for you to do together and go on all these lovely weekend retreats where you are told that if you hang out with someone who's not a loyal follower of The Guru then it would be very bad for your karma.
The unanimity and the single leadership make cults different in kind, and not just different in degree, from other kinds of organized goal-seeking human groups. And I really don't see how the cult model, seen in this way, applies to YC.
With over 22000 karma points, (~5000 more than nickb) you could construe that Paul Graham is the cult leader of this board, whereby his words are not just approved, they are also a guide.
If you start disagreeing with PG in a large way, those that like him will scrutinize you and take aim as they may feel they are also being questioned. So there is a slight cultish behaviour going on with this board and maybe with its larger YCombinator fund context, but not intently by PG, he's an investor for the most part.
YCombinator as a 'startup scene' is not a cult because no harm is being done, and the absorption of minds is for the most part very beneficial. Cult leaders, I think take advantage of their own charisma to defray free choice in their environment for their own benefit. All in all, Ycombinator has a culture but is not a cult.
The notion "build something people want" I think is an ideology and ideologies are at the foundations of many cults, but cults generally have spiritual or religious overtones.
E.g. you give all your money to The Guru because that's what a loyal follower of The Guru does, and all the people you hang out with are loyal followers of The Guru. All the people you hang out with are loyal followers of The Guru because they love you so much and they have so many things for you to do together and go on all these lovely weekend retreats where you are told that if you hang out with someone who's not a loyal follower of The Guru then it would be very bad for your karma.
The unanimity and the single leadership make cults different in kind, and not just different in degree, from other kinds of organized goal-seeking human groups. And I really don't see how the cult model, seen in this way, applies to YC.