It's an extremely interesting theory backed up by some pretty solid evidence, not only that but have you ever been in a situation where someone you know, knows someone that you've seen or heard about on TV or wherever. It's a small world really..
To op though, Yeah, I've heard of this before. It really makes sense but in order to actually follow the 6 degrees, you get to know more people, therefore decreasing the number of degrees between any two people. It's pretty intense actually.