Links are one of the most discussed topics in the SEO world. The ideas about link value, page rank, and anchor text are more or less formed until the search engines force the definitions to change. However, Rand Fishkin has an interesting post about the relevancy of link value for the domain (not the page) and the rate of growth of links.
The general assumption in link building is that a quality link transfers value to the page that it is linked to. The assumption is only partly true as the link value is also transferred to other pages on the domain. As it happens, some domains gain authority as whole due to the cumulative value of incoming links. This value is in turn transferred to each page on the domain. Some interesting examples are cited, such as About.com, Technorati, Expedia, Del.icio.us. Rand has presented the idea of "rising tide lifts all ships."
However, there seems to be another factor which I think can be crucial for transfer of link value. The factor is of interlinking. For the rising tide to lift the ship, it has to be a tightly bound ship in the first place not a loose flotilla. This is where interlinking plays an important role. The value flows more evenly throughout the domain knitting it together. Too many sub-domains, messy sub-folders are hindrances to free flow of the link value internally.
The other point in the post is the rate of growth of links. This is what I found to be truly interesting. Remember, the bugs in Matrix movie – they can see you only when you move or are active in any way. That’s the catch: activity levels. In the online world, activity levels are detected by the rate of links (and regularity of posting, content addition/update, page additions, frequency of code tweaks etc.)
Go to the post by Rand.