I also thought immediately of that xkcd. I'm glad you posted it.

I'd like an explanation of what this ID would entail and what problem it solves. At the moment with MyGov, I control my ID. I tell them my email address or phone number. Things I can change. Different government agencies can link into my MyGov ID. I think this system works well.

I don't know what is wrong with the status quo. So, I am not informed enough to argue for/against some other ID.