First, people have multiple parts of their lives, and they don't want them to mix. There are many reasons why this is good, but at the very least let's observe that this is how most people arrange their lives. There's work, and there's play. On the Internet, pseudonyms allow these separate lives to be separated more effectively.
Second, it fights prejudice. What makes prejudice so bad is not just that people are judged wrongly, but that they are judged wrongly using information that really should be irrelevant. Using pseudonyms means that this irrelevant information can be completely non-present. If your name is Julie or Juan or Duk-Kwan, you can expect to get a different--unfairly different--reaction if people learn your name, and thus your probable gender or ethnicity.
Finally, let me emphasize that pseudonyms are not anonymous. They are actual names, and they accumulate a reputation just like any other name. "Tom Cruise" is a pseudonym, but it's a name that has a very strong reputation (of one sort or another). So it goes with online pseudonyms, as well.
Given this, readers won't be surprised that I oppose Blizzard's trend toward using a "real" ID, "real" meaning a name on the credit card that pays for an account. Already, if you want to participate in cross-server chat on their games, you have to expose your credit-card name to everyone on your cross-server friends list. Now they are talking about changing the official forums to use credit-card names rather than
The idea seams to be that if people post under their credit-card names rather than their Warcraft character names, then they'll post better content to the forums. I don't agree this is a sufficient reason for the change, and I don't even think they are going to get the result the hope for.
Aside from all this heavy stuff, why in the world is a fantasy online computer game going this way? Grey Shade says it best:
But that’s it, you get it? That’s why I play. That’s why my friends play. Because we like to come home from a long day of being John Smith or Jane Doe and get on the computer and MURDER SOME REALLY AWESOME INTERNET DRAGONS.
UPDATE: Blizzard cancelled enforced real names on the forums, and said they are going to strive to prevent real names leaking in-game for people who want that. Good choices! Crisis averted. Everyone can go back, now, to killing Internet dragons.