also just recently asked a similar question, or rather first, a slightly more advanced option — do I need a nickname at all if emeil for a login, first name+last Name for display on the website in the form of(Bob P.), came to the conclusion that you still need for more human identification in the user profile. so the url was /profile/id123456, a /profile/nickname is no copngrats creates on a server and users with clear and convenient. Well, now to answer your question — it all depends on the type of site and authorization methods on it. If the nickname used for login is better not to allow to change it, if just to display on the website(Display Name in forums IPB and vBulletin) — why not, the important thing to knowing the current nickname you could always tell the user, well, any functionality(such as bans) was not tied to the nickname. And last, it is important to design the database and the logic to avoid unnecessary queries.