The 'Blurt' button on Blurtit allows you to share a question or answer you've enjoyed with everyone that is following you.
For example, I 'Blurter' Raul Stewart's great answer above, and now everyone that is following my account will be able to see his answer in their home feed too.
I think it means they like what you wrote.
"Blurt" is another way to say share. So you may blurt a question if it's thought-provoking or an answer if it makes a really good point and whatnot. And your followers get to see whatever you blurt.
I guess it's like Facebook in a sense, where you can share peoples' statuses and your friends can see it. That's one thing that Yahoo! Answers doesn't have that Blurtit does - sharing (or at least I think).