<i>"... We have sparse data about ycombinator.com, so these are rough estimates ..."</i><p>Cynical enough to reckon the algorythm skews results on un-paid customers?
If you ever needed an example of what is wrong w/ all the panel-based demographic and analytics info sites - this is it.<p>This kind of methodology works fine if you are analyzing a very very large site that many people use (facebook, myspace, etc). It's old thinking to think that a panel of people can accurately measure niche content. It might work for nielsen on TV, but it obviously is completely broken for web sites.
Here's a service that gives an alternate take -- though also with dubious, thin info, and only on '<a href="http://ycombinator.com'" rel="nofollow">http://ycombinator.com'</a> not '<a href="http://news.ycombinator.com'" rel="nofollow">http://news.ycombinator.com'</a>:<p><a href="http://adlab.msn.com/DPUI/DPUI.aspx" rel="nofollow">http://adlab.msn.com/DPUI/DPUI.aspx</a>