Link building is a vital part of search engine optimisation, however one should be aware of what a Google engineer described as Google Bombing.

This occurs when the algo picks up a sudden increase in links to a site. The site will disappear down the SERPS for a while, as G regards it as unnatural linking.

One can test this by taking a site that has had a search term as No.1 for quite some time, and bang in a load more links, and then watch the effect.

This effect is also noticed in MSN and Yahoo.