Some people seem to think they are not.
http://www.intotheminds.com/blog/en/recommendation-algorithms-the-myth-of-filter-bubbles-at-stake/ (http://www.intotheminds.com/blog/en/recommendation-algorithms-the-myth-of-filter-bubbles-at-stake/)
Not a position I'd considered! -- I mean, filter bubbles exist, that's not debatable, I think the question is to what degree they actually influence us?
I'd like to read some of those papers.