"The internet is written in ink."
Astute observation, Mister Sorkin. I don't know about the rest of the internet users, but change can be a good thing, sometimes. Often, it's necessary, especially when you want to make a fresh start. We change through a lot as we grow older, tastes in food, clothing, music, movies, etc. Why can't our usernames be given the same option?
Don't get me wrong, I still Final Fantasy VII to death, and it's a game I still love to play from time to time, but I think my handle "OmnislashMaster" doesn't work for an internet alias anymore. Yet many sites prevent a username change. DevART forces you to upgrade to Premium in order to change. Hell, Google doesn't allow you to create alias accounts that share a parent email address.
Now, to be fair, I have no idea if incorporating the option to change a username has a profound affect on a site's resources, so there may very well be a reason why many sites refrain from allowing users to change their internet handle. Even so, why not limit username changes once every two months or something?