Googel+ was by far the best social network I've ever seen, the only one I've got addicted to and the only one I've actually written posts to. All Google had to do with it was adding youtube-like recommendations (many people complained it was "empty" while I had a waterfall of great content in it just because I actually subscribed to everybody I could discover, to those they were subscribed to etc) and leave it as it was without introducing more and more complicated concepts.