Ebay.de, Preisvergleich.de and others belong to Adword SearchNetwork, so you could be listed via keywords you pay for (not as a product itself but as advertisment on that pages). So if you use urls like www.domain.xy/?pk_campaign=Adwords (without pk_kwd) in your Adwords campaigns, Piwik will check the referer to determine the real searched keyword, and adding this pages to searchengines datafile would allow piwik to guess the keyword for this pages, too. Add the moment piwik shows only the url "www.ebay.de" but that's not really useful. And if you use pk_kwd in Adwords Campaign you only get the keyword you added, not the real searched one.