I just found an interesting counterpart to the "why authors are sometimes pseudonymous" and "why leftists are sometimes pseudonymous" bits in a blog entry by Dominion, aka James McLaughlin. The article deals with several points that have already been common bones of contention (like whether or not a "real name" grants one any more credibility and situations where pseudonymity or anonymity aren't really an option), but brings up two points that are worthy of highlighting.

First, he notes:

most of us old timers are pseudonymous because back in the day it was considered none to wise to allow personal information of any sort to escape over the internet. See most of us came from the land of the Bulletin Board System (BBS). A BBS was sort of like a combination of usenet (people would post in what were known as SIGS or Special Interest Groups) they would play what were called door games (people would log, make a series of moves that day, then observe the actions and reactions of the other players the next day) and sometimes chat. They were usually local, set up on someone's personal PC. Since they were local, it was highly advised that you did not share personal information over the system. We used what were called "nyms" or "handles" instead of our real names. A lot of that suspicion leaked over when we moved to the internet, the worldwide implications not really striking us yet. I came up with the nym Dominion back in the day I was posting to WWIVNet and it has stuck with me though thick and thin.

It's been rather a long time since the BBS days, but the admonishment to keep personal information off the network, any network, stuck and was one of the big reasons why the cypherpunks gained relative cachet and importance throughout most of the last decade. I've been using this handle (and a few others) since the BBS days, and I remember boards that told you under no uncertain terms to keep personal information to yourself, and practically nobody used their real names on Fidonet.

Second is perhaps the best and most chilling example of how the Internet is here:

Nor should anyone discount the actual danger of people knowing who you are. Take, for example, Grady Ward and Dennis Erlich. Dennis Erlich was a high official in the Church of Scientology. Grady was merely a critic. Both of them had their doors busted down by cops, had their computers confiscated, had the peace of their life shattered, had lawsuits brought against them, supposedly for posting the Church's Stupid Sekret Skripture, but really for the crime of daring to criticize the Church.

For those who don't know, the usenet group alt.religion.scientology was largely populated by fierce critics of the Church of Scientology, and the Church wasn't happy about it in the slightest. (They don't, as a rule, like criticism much.) Past critics of the Church have gone through hell as the Church does whatever is within its power to discredit, embarrass, and intimidate those who set themselves in opposition to it, and for a while there was no greater opposition to the Church than the denizens of that newsgroup. It was through anonymous postings on that newsgroup that people found out about some of the odder, science-fictionesque material that forms the basis of high-level Scientology, and it was through the attempt to track down the anonymous posters of these materials that the Church managed to bring down "anon.penet.fi"... the biggest anonymous email remailer in the world back then.

To this day the newsgroup remains a battleground between the Church's detractors and supporters, and the only reason it remains so is because the Church can't take the battle to "IRL".

In any case, it's a good entry- I highly recommend it.