I think the really interesting thing about the alumni network is that it's not only growing in size, but experience. At this point there are companies inside of YC that have grown larger and been around longer than Viaweb was, so not only are you able to get advice from folks other than the YC founders, there's an emerging set of people who are in some aspects more experienced. (Though, naturally none who have seen more early phase startups up close.)

That's one of those surprising emergent properties that I think will be of increasing import as the trend continues upwards and also has an effect of distributing the load on the YC founders.