CainIV - 7:31 am on Feb 22, 2010 (gmt 0)
And never forget the value of being an authority.
One very large authority I see in many markets is actively purchases many, many links - thousands that are labeled sponsored links on higher pr websites that actively display link advertising and rates. Their rankings simply improve month to month for huge one - one, two and three keyword phrases. Anyone who spends time analyzing backlinks consistently every day in ecommerce has likely seen them and their fine body of work :)
A fraction of these links secured for a smaller website would look completely unnatural. But for this authority, they are a small - although laser targeted - percentage of the overall number of links to the website.
So, of course, the way link buys are calculated and applied to websites is also different depending on a likely large number of further factors.