I started using "rjbs" as my identifier everywhere a few years ago. It was a very good idea, and I should have started using it years earlier. I've given a fairly detailed history of other usernames I used in the past elsewhere. I'll move that history to my wiki at some point, I guess. I just got to thinking about "rjbs" and other actually-related-to-my-name names on Thanksgiving, when talking with my Uncle Richard.
He said, "Hey, did you have an account with $Financial_Institution?" I did, and told him so, and he said that it was the only place he'd ever tried to get "rsignes" and failed. I laughed and said that I only used "rsignes" on those obnoxious sites which require usernames of six or more characters. (I guess I'd use it if five characters were required, too, but I've never seen that.)
I can't recall when I first started using "rjbs," anymore. IRC logs suggest it was March 2002. I know it was after I started at IQE, though, because I would've pushed to use "rjbs" as my primary login. Instead, I got the generic first-initial-and-last-name that nearly all Win32 users are subjected to in offices. Well, that's probably a corporate thing and not a Windows thing, but that's not the point. Since I was using it at work, I got pretty used to seeing "rsignes." I wasn't using "rsignes" for anything else important, so work was really the place that drove it home.
Then I found out that my co-worker and friend Brian used "rignes" as his username all over the place. At first, I was sure he was just trying to irritate me, but then he explained it to me. Once upon a time, when Magic: the Gathering was young, he used the username Sengir, like the "Tim the Magician" card. Magic got too popular, though, and Sengir was always taken, so he just spelled it backwards.
Even now, I see "rignes" mocking me on IRC and it's then I feel the stranger kick me right between the eyes. (Sorry.) It's even worse than the flashes back to sibling ridicule that occur when someone quotes Dominus and calls me (or someone nearby) "Retardo."
To sum up: if you are writing a big system that I might have to use, please consider allowing four-character usernames. If you control a large system where "rjbs" is taken by someone who isn't me (AIM, hint hint), please delete or reprovision the account and let me know.
Oh, and one last thing: if you are going to send me a request for donations (Boston U, I'm looking at you), please spell my name right. There is an accent on the in Julin.