Neil Patel at Link Building blog has written about building links through YouTube. Neil says that many sites have incoming links from YouTube. It is possible that YouTube links back if your site is amongst the top five sites that drives maximum traffic to a video on YouTube.
However, all the comments to this post have a similar story to tell that YouTube links are all nofollow. Is it really possible that Neil could have missed the 'nofollow' point or he is simply trying to convey a different message. Let's hope he gets back on it.