Site-wide links can hurt your rankings

If a site links to another site from every page, those links are called site-wide links. If you are buying links, it may look as a good option to receive hundreds of incoming backlinks for the price of one link, however, most search engines would count only the most powerful link which is relevant. Site-wide links also make your link profile to look artificial, as you’d have hundreds of incoming links with the sama anchor text. Many SEO forums have reported that side-wide links can actually hurt your ranking in search engines like Google, especially when site-wide links constitute a large percentage of the incoming links.

If most of your link popularity comes from purchased site-wide links, Google will eventually find and eliminate the value of these links. So it is advisable to buy few single links that would fly under the radar.

However, it makes me wonder how Google treats blogroll links. Most blogroll links, by default, are site-wide links – Going by the logic of anchor text, it would mean that it is better not to receive blogroll links from huge blogs having hundreds of pages.

Resources : http://www.google-success.com/site-wide-links-can-hurt-your-rankings.htm