CogBlog

Rand at SEOMozBlog published an interesting post on the relative value of various SEO tactics depending on the age and maturity of your website.

Here's one:


This chart shows how the value of on-page optimization declines as the level of competition in the search results increases, and that at a certain point a SE will begin relying more heavily on inbound links to determine position than on on-page/site factors to determine position. This jives with our own experience with the relative importance of these tactics.

Several other good charts in the full article here.