Jed (the source spreadsheet maintainer) does a really good job of keeping the newer companies up to date with public info, but it's hard to find a lot of public info on YC companies before the fact that they were YC was newsworthy.
I agree, but it's probably up to the founders and pg how much information they make public, more so from the founders. It'd be interesting to see someone publish their quarterly earnings akin to what balsamiq did awhile back (http://blogs.balsamiq.com/product//2010/01/03/a-look-back-at...).
Does someone have Jed's contact details, I did a lot of research on this for a blog post a while back, probably makes sense for me send some of the corrections his way.