All of this is quite important because search is so central to how people navigate the Internet, and because advertising is the main monetization mechanism for a wide range of Web sites and Web services. Both search and online advertising are increasingly controlled by a single firm, Google. That can be a problem because Google’s business is helped along by significant network effects (just like the PC operating system business). Search engine algorithms “learn” by observing how users interact with search results. Google’s algorithms learn less common search terms better than others because many more people are conducting searches on these terms on Google.

These and other network effects make it hard for competing search engines to catch up. Microsoft’s well-received Bing search engine is addressing this challenge by offering innovations in areas that are less dependent on volume. But Bing needs to gain volume too, in order to increase the relevance of search results for less common search terms. That is why Microsoft and Yahoo! are combining their search volumes. And that is why we are concerned about Google business practices that tend to lock in publishers and advertisers and make it harder for Microsoft to gain search volume.

via Competition Authorities and Search – Microsoft On The Issues.