I think people are overlooking the fact that everyone has always lived in a filter bubble. There's an undeniable influence of your surroundings on your beliefs and knowledge about the world. To follow up on the example Berners-Lee gives: rich people are already unaware of the existence of cheap alternatives. On a fundamental level, they know they exist (if not because of direct contact, then because of fundamental knowledge of the way society works), but on a practical level, these alternatives aren't considered and they aren't advertised by their friends or by the media the rich consume.

People are only more broadly aware if they are open for, and looking for, alternative information. This has always been the case.