Have you tried searching for a business in Google lately? If you have, you know that the search results are often cluttered with page after page of Yelp clones and Yellow Pages knock-offs. If you want a review of, say, a local pizza place, you want real content, not a hundred sites each of which contains nothing more than a generic blurb, the pizza place's phone number and address and maybe (if you're lucky) a few barely-readable, one-line user reviews.
A search for amelio's montreal pizza review, for instance, returns links to yelp.ca, urbanspoon.com, tripadvisor.ca, 411.ca...In fact, the first two pages of the search contain (in my opinion), 15 junk results and only 5 decent ones.
Solutions do exist to filter your Google search results. You can permanently block websites through your Google account—but what if you only want to hide certain sites sometimes? You can use browser add-ons to hide results from certain sites—but they just hide them, so you get back half-empty pages of results (nothing makes you lose confidence in the web faster than seeing three pages of results in a row where EVERY single result is hidden). You can add -site tags to your Google queries, but when you want to block a hundred sites or more, that becomes ridiculous. The solution? Google Filter!