That Staples varies its prices dependent on your distance to an Office Depot is the very argument infavour of allowing the big box stores like WalMart to set up where ever.
He fears this will mean that we don't get to see information that challenges our world view, and will ultimately be bad for democracy - if you're an American infavour of gun control, for instance, you will tend to see information that reflects your views, while members of the National Rifle Association will be served up sites that chime with their stance.