That's not yet used by all browsers. And it's a bit more restrictive than necessary, since the base domain is supposed to not be a website at all (and loses the

That's not yet used by all browsers. And it's a bit more restrictive than necessary, since the base domain is supposed to not be a website at all (and loses the ability to do some things with cookies iirc). That's not always the case. co.uk doesn't need to set cookies, but blogspot.com does (and is a website), so .blogspot.com can't be an eTLD.