People shouldn't be allowed to change their nicks.
I agree, partially. But if you make a typing error, you'll never be able to correct it. They should have a system where you may change you nickname, but it will show a little message showing who you were previously for a few months. That way by the time the nickname is changed, everyone will know who that person is. Also, name-changing could be banned for a short period for a user if he changed his nickname >3 times in the past week, etc.