I have heard of that, and I think that's accurate for a lot of mainstream sites. I'd go a step further and say they have different "categories" of the internet that they sort you into based on your "profile" online, whether based on geographic area or search history. So depending on where you live or what arbitrary "category" they put you into, you might see a slightly different internet from everyone else. Don't have any real evidence to prove that, just a gut feeling.