impact factors and search engine coverage

There is an increasing amount of academic and other information on the web [1]. There is also an increasing number of online journals as well as online versions and indices of traditional journals. It seems natural therefore to expand the notion of Impact Factors for journals to web equivalents, and to use the power of search engines to carefully extend them to cover other domains on the Internet. However, search engines only index a proportion of the web, and this proportion is not determined randomly but by following algorithms that take into account the very properties that Impact Factors measure. A survey was conducted in order test the coverage of search engines and to decide whether their partial coverage is indeed an obstacle to using them to calculate Web Impact Factors. The results indicate that search engine coverage, even of large national domains is extremely uneven and would be likely to lead to misleading calculations