Dunbar's number generally applies to communities that are organized around content or ideology.<p>So for example, a web forum gets too large for everyone to agree on what's on topic or off topic, so it splits in two. Or a democratically run government can't agree on whether the society should be gemeinschaft or gezellschaft.<p>The YC network is more like a dating site than a polis, so while there may be some limiting factor I don't think it would be Dunbar's number.