What are “filter bubbles” and why does Pariser believe they are a danger?

1. Please watch Eli Pariser’s video: “Beware Online Filter Bubbles”

https://www.ted.com/talks/eli_pariser_beware_online_filter_bubbles

What are “filter bubbles” and why does Pariser believe they are a danger? In your opinion, is part of being information literate understanding ways to circumvent “well-meaning” personalized web searches? If so, how might that be accomplished? What do we risk by accepting, without question, what appears in answer to our Google or other Internet searches?