Why Can’t I Comment on YouTube?
YouTube, which is owned by Google, made substantial changes to their commenting feature this week. and if you've tried to comment on a YouTube video, you may have noticed some changes.
Chief among those changes is that commenting on YouTube now requires a Google+ account. Google+ is a fledgling social network looking to gain market share against Facebook and Twitter.
This text appears as a pop-up in the Comments section of YouTube:
See more from people you know.Meaningful conversations
New threaded format and +mentions encourage discussion.In more places
Comments appear from both YouTube and Google+.