I also don't see what the big deal is. Having a Wikipedia article does not all of a sudden validate the Y Combinator idea, and having it deleted certainly does not invalidate the work they've done.

To put it in perspective, ignition partners, one of the largest north western venture capital funds, does not have a wikipedia page.

Take a look at the articles on VC firms on sand hill:

http://en.wikipedia.org/wiki/Sand_Hill_Road

Only KPCB has an informative, encyclopedic entry - the rest I would argue don't even need to have articles.

Not to mention YC isn't a big VC firm, it's seed-only.