Site wide links have long been utilised by website groups as a way of doing some quick and pain-free link building.
Many SEOs have already realised their value was questionable but it takes a long time for new ideas to filter into other departments.
However we now have credible sources to prove they provide very little, if any.
Matt Cutts was interviewed recently by Danny Sullivan at SMX Advanced in Seattle and said…
We’ve done a good job of ignoring boilerplate, site wide links.
Bing also announced something similar in a recent blog post.
Site wide links often happen, and while they can be beneficial in terms of maybe driving direct traffic to your site, they are much less useful for organic ranking. A site wide link is less of an endorsement than being mentioned in the body copy of the page.
Whilst site wide links may provide some cross-brand exposure, don’t think they’re helping out with SEO performance.
Website groups are best minimising large volumes of links to home pages and try to generate as many relevant, varied and deep linking.