If anyone does something like this, I'd suggest supporting not just http://junk.launchpad.net/~jmillikin/ but also something like http://junk.launchpad.net/~~jmillikinpersonalwebsite.com/ , embedding other domain names in URLs for your service (with a policy of only permitting people to set up such double-tilde URLs in your service when they control the corresponding domain). Then to the extent that your service ever enjoys a success disaster where newbies naturally discover that all the mnemonic usernames like newman and whn and wnewman are already taken, you have relieved the pressure by providing a mechanism to delegate the unique name problem to the existing domain name system.