Page Share - Web Analytic Concept

It's been a theme lately on various blogs to discuss metric called page share. The idea of page share is that a weighting measurement is put on the various real estate of a web page. That weighting is based on the location of the page and also it's ability to get clicks and conversions. Greg theorizes it would then be easy to calculate how much ad units should sell for or what space is worth because if we know the total page's CPM value, we could sell space on the page by multiplying the weighting by the total CPM value. This concept would have worked nicely for me when I was selling a lot of direct advertising for one of my past sites. I often was arbitrarily picking prices for various ad units without really much reason behind it.