In random graphs theory there is an interesting phenomenon called percolation. It basically says that when you have a very large random graph, depending on the average of the local structure (i.e. how many links each node have), you can determine some properties with respect to the general connectivity of the graph, and the number of hops you need to get from one node to the next. High percolation value means few hops are needed to navigate between to different ideas.
What the mathematical theory says is that depending on the local structure, there is a strong threshold effect where if you had just a little more local connectivity, you would need exponentially less hops to reach any other node in average.
"Filter bubbles" are appearing because by a clever choice of (search engine) personnalization policies we are now losing the high percolation value.
It results from the algorithms used inside search engines, which analyses your online behavior, and decides to push you the information, you will most likely enjoy. Infomation is now personalized so much that when you search for something, you will probably only find something that shares your point of view with regard to the subject you searched, which will tend to confort you on your own perspective, but at the same time, you are less and less confronted with opposite perspectives.
This bias is particulary hard to avoid, and is self reinforcing, because of economic interest of various actors. I think it's becoming increasingly overwhelming these days mainly because of another bias of search engines, which is ultra-specialization. Most search-engine-visible websites, are now ultra specific to your query. This mean that when you have visited one page of the website you will most likely go back to the search engine, rather than following a link on the website to an unrelated surprisingly interessant subject.
How to avoid them : As a user the cleanest way to avoid getting trapped in a filter bubble is to have control on the filter. Unfortunately, that's not something search-engines offer for now.
As a user, being aware of them and searching for a wide variety of point of views is a good step. You can also start following some website that spreads ideas on various unrelated subjects. Would the percolation number be higher would I recommend to follow links rather than using search engines.
Social medias, are not an answer to this phenomenon, as friends and communities typically show a strong cluster-like behaviour.
As a blogger, if you feel the courage (massive de-ranking is previsible), you can contribute by diversifying your blog so you could expose to a wider variety of subjects.
