A long standing complaint that I have had with search engines is that they disgorge a lot of irrelevant results in the form of sales pitches. Of particular concern, when searching for for product reviews, you get websites that do not have real reviews and in some cases don't even have the product! Yet you are stuck wading through this morass looking for that proverbial needle.
Of course, to be fair, these search engines would not exist if it were not the for the fact that companies are paying the search engines for this advertising. Nevertheless, it is a disservice to simply dump on the user irrelevant content. After a while, the user will get discouraged and simply not use the search engine. Displaying relevant results, in the end will promote business and user satisfaction/trust will be a lot higher. Ubersoft has an excellent cartoon related to Microsoft's new search engine Bing, that also highlights the detrimental effects of giving the user irrelevant results. (To see the image better, click on it or on the word Ubersoft.)