How to get blurred backrounds in videos?

How would I get blurred backrounds on videos, make it look professional looking, like shane dawsons, or wheezy waiter. What would be the best way to do this? Thanks.

Example: http://www.youtube.com/watch?v=R-6rDLJlGCI

From 0:00 to 0:08 is the kind of effect I want.
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