I have written several times about how using a pseudonym online is one way to maintain privacy and security. Writers and artists have done this for centuries, either to protect their privacy, or to be able to focus on one genre at at time (someone who writes both horror fiction and documentaries, for example, might use different professional names for each pursuit), or because their real name is not very memorable or someone else has already become famous with that name. People also sometimes do business under names other than their own, and these names sometimes registered as "DBAs" (doing business as), or "ficticious names." The names, when used correctly, represent real-life people, who intend to be responsible for all of the activity they do under that name.
What is not acceptable, is when someone creates one of these names to impersonate a real-life person, or to engage in unethical or illegal activity without getting caught. This problem of "imposter profiles" that sometimes arrises on the popular social networking site, Facebook.
A friend of mine (not a famous person) recently had her profile duplicated after signing up for one of the games on Facebook. The imposter copied her profile image, and her name (one character different from the name she was using). She believes this was done for phishing purposes, either to try to get her passwords, and/or to spam her friends. She followed the instructions, HERE for reporting this account, and was disabled pretty quickly.
This was a concern for the Facebook administrators which has disabled more than once the account of a person who, unfortunately, has the same name as Facebook's founder, Mark Zuckerberg. This is actually the man's real name, and because he's older than the creator of Facebook, it was actually his name first. While he is handling this with a lot more grace and humor than I probably would have, one can easily see the need for the Facebook admins to protect their well-known founder. It would be too easy for someone to scam A LOT of people using Mark Zuckerberg's (the famous one's) name.
Bottom line? Pseudonyms are generally acceptable, as long as they are used for legitimate purposes, and the person behind the pseudonym takes personal responsibility for the activity they do under that name. Imposter accounts are NOT acceptable on Facebook or anywhere else, if they're being created to harrass, humiliate, or defame others, or if the person who created the pseudonym is hiding behind the account to do unethical, illegal, immoral or other dubious activity.
Jennifer Pointer (e-mail) is in Tulsa, OK. She promotes a simple, a low-tech approach to effective online profile management, search engine optimization and social networking.