I cannot register with my nickname in a LOT of online services/games. Sony even sent me a scary letter with intention to suspend account.

Also I utterly hate all those online services that require at least 6 letters in nickname...

I think that's why an online card game I play won't let me name my tarot-themed deck "Tarot", it changes it to "*ot". Not sure what it means but I guess their censoring mechanism taught me a new slur?