For some reason, Google added a YouTube contact group to many Gmail accounts. I currently have 82 contacts in the YouTube group and they have only one thing in common: they sent me or I sent them an email in 2006, 2007 or 2008. They don't have anything to do with YouTube and some of the email addresses couldn't be used to create Google accounts (for example, the Writely email address for importing documents).
The YouTube group can be renamed or deleted, but it's strange that it was automatically created. Gmail has some
system groups for Google Latitude, Google Talk, Google Buzz, but they're hidden and can't be removed.
Do you see the YouTube group in your Gmail account?
{ Thanks, Katty and
everyone who commented on Google+. }