Aron Wall, author of the recommendable SEO-book, is calling attention to the increasing abuse of subdomains through the “big ones”. Because Google grants the strength or rather the trust of a domain such a farreaching role in rating the relevance of their results, it often is the case that more than one subpages for a query will be found and displayed on one page. To minimize this, Google will only allow a maximum of two sites from one host to be displayed on one resultspage, where the second result is already indented and all the others will only be displayed when the [More results from example.org] link is clicked. The problem here is that Google is only combining results for the exact same hostnames, www.sistrix.com for example is already a different host than tools.sistrix.com.

Where this can lead to is shown exemplary by a search for [Reinigungsservice Kleinanzeigen (cleaners classifieds)] – of the first 100 results, 95 are hosted on the kijiji.de domain – colored red on the screenshot to the right. The diversity, which Google likes to call to attention whenever possible, that should be found in the Google-SERPs is gone completely. Kijiji's parent company Ebay seems to also be well aware of the possibilities which are enabled though a targeted use of strong subdomains. The indexing of search.ebay.de should not be in agreement with Google's-webmaster-guidelines which recommend to prevent the indexing of searchresults. An additional subdomain where the added value for the customer is hard to grasp is kaufen.ebay.de. But we also have companies like Yahoo, whose traffic should come to a not-so-little part from the Google-index, who are occupying many positions of some searches with a multitude of subdomains. Someone who proves that there is also another way is Wikipedia: one one subdomain per language.

The accusation here should not only be made out to those who are using these loopholes, but also Google itself. This problem is known for a few years already and it is about time that Google comes up with an intelligent summarization of subdomains.