Journal: Online user names

I've been working on changing my online nick across every site I've been using. Unfortunately, this means creating new accounts everywhere and generally losing my history. I wish all sites worked more like LiveJournal, where it is possible (though not easy) to change your user name, as long as the new user name is available. I really wish Slashdot had a similar method. I wonder why more sites don't have the option to change your user name...