Sony has been rather strict with the username violations that can occur on their PlayStation Network service however things can change pretty quickly so it is possible that an account name that was possible on the PS3 is outright banned on the PS4. This has now led to an unfair ban for one such user who created his PSN account 8 years ago and was banned by Sony just recently.
Reddit user tiago28peixoto created this PSN username when he was only 12 and he admits that it was a stupid username, however he was too young to realize it back then. He recounts his experience in a thread on reddit.
This morning I received an e-mail from PlayStation informing me that my account was permanently banned due to violations of the PlayStation Network Terms. Of course they didn’t bother to inform me in the e-mail why exactly I was banned so I had to call PlayStation Support. In that call they told me that my account I was banned for life because my online ID violates the Code of Conduct. My online ID is (was) KingMADAFAKA. I admit that it is a stupid username, but I created when I was only 12. I asked them if there was a way to change the username in order not to loose every game that I had on my account (my FIFA account was amazing, I had a really good Ultimate Team) and all the money that I invested in the account, but they said that I can not change the online ID, therefore my account is banned for life and I have to create a new one from scratch.
The issue with the name aside, it is still a backwards move that Sony has yet to allow username change for PlayStation Network. If you have made a username when you were young and consider it stupid or offensive, you will remain stuck with it until Sony can decide it is time to implement username change. Microsoft offers username change and the same is the case for Nintendo, however they are still restricted by a certain time limit compared to basically nothing from Sony.