Dave Sifry, founder of Technorati, a specialised internet search engine, knows what it is like to fall foul of Google's algorithm.

Like many businesses that live on the web, Technorati relies heavily on traffic directed its way by Google. The internet group has also become a competitor, creating a service of its own to search inside blogs – the same market that Technorati was set up to serve. Technorati's standing in the all-important Google search rankings have tumbled on several occasions, says Mr Sifry, hitting its business directly.

“We were certainly penalised,” he says of the relegation. He adds that he does not know whether his company was singled out for special treatment, or whether it fell foul of a broader change to Google's search technology that also hit other similar websites.