That's really a good question that I've pondered many times. The answer depends on what kind of person you are and what the motives for identity change would be. Most people that have to go as far as changing their identity are obviously disliked or have done something wrong. In this case, creating a new identity is questionable. However, it's not the name, it's the behavior. Changing your name and then behaving perfectly would not be as much pretending you are someone else and tricking people into trusting you as much as restarting with a clean slate without the burden of people who already judged you when you were using your other name.

Of course, if you're liked and just want to do it to escape yourself for a while (online of course), I can't really see anything that could be wrong with it.

Lastly, if it's so you can do something wrong in your new identity it is, of course, the wrong thing to do. But, really, changing your identity (or, to a lesser extent, making an aka like I use "Zypher" as) is completely right.

That's just my opinion. It depends on the case and personal opinion. If someone wants to start using a clean slate with the purpose of being nice without still being pressured by people that believe they won't change and associate their old name with whatever bad act they preformed, I have nothing against it. It really depends on who you ask. As with any opinion, there is no "correct answer."