Lots of people use the nice hostnames like ftp.us.debian.org. It wouldn't be too hard to get included in that host name if you're determined. I haven't looked into the requirements, but I'm pretty sure it's a) be technically competent enough to run a mirror (it's not hard) b) have a lot of bandwidth. c) be organizationally competent enough to convince Debian that a and b will hold for a long time.