In 3.1 a youtube profilefield was added in which we can insert our youtube username to link to it.... There is just one major problem though...

New youtube members no longer get an username. So I think we should decide on providing different ways to access their profile.

More details can be found in the discussion on area51:
https://area51.phpbb.com/phpBB/viewtopic.php?f=81&t=47726