Once someone sees a username on one site, they'll try to see if it's open on another.
It's happened to me twice. There was even a time I changed my username on Gaia and someone took my old name a day later; everyone thought that person was me.
I dunno, I'm just really um... OCD about things like that? Like, all of my social sites have to be updated with the same e-mail and username if I am actively using them or my brain hurts crying
I guess I'm crazy emo
That's why I use comments, some people don't like to though because comments are public and w/e
urgh I wanna make my new account but I don't want anyone stealing the username I chose for anything like on DA or something >~>
I wanna play zomg all over again xD