Alan Wexelblat writes: [Asks, why is anonymity/pseudonymity useful when posting?]
Case 1) technical postings of a research/white (in the sense of whitenet/ blacknet) nature. Here anonymity would be a hindrance. I post in large part to help my name be known in certain academic circles. In this case I would tend to wonder at people who posted anonymously and would (as was mentioned in this list) tend to discount their information. In research circles, name value means a lot.
An anonymous/pseudonymous poster may want to expose faulty reasoning or research methods on the part of a previous poster, where that poster is their boss, faculty advisor, department chair, [employee of] generous donor to a nonprofit org .. etc. This is also useful for revealing insider information of a sensitive or "whistleblowing" nature; see below.
Case 2) technical postings of a black nature. Here anonymity is a big help, as you may have some question about the legality of what you are doing. But the question I have is: why post at all? What gain is there from publicizing this kind of information? Perhaps the gain is some assurance of safety from retaliation from parties who might feel themselves wronged by what you posted. In this case, anonymity wins.
This is useful for posting security holes that CERT/vendors won't acknowledge or address; it seems generally useful when posting something that might get you (a) fired or (b) sued. Consider the (ongoing, I think) litigation against the person who posted negative comments about a stock to Prodigy. SLAPP (strategic lawsuit against public participants) actions aren't (to my limited knowledge) common in the online world, but aren't so uncommon in, say, logging-protest world. Even where a SLAPP suit isn't successful (in terms of a favorable verdict), they can be very burdensome to defendants. (The suit against the poster to Prodigy may or may not be a real SLAPP, but it's at least similar.)
Case 3) non-technical postings (social, talk). Again I wonder what is the value of anonymity in this case. To have a social conversation is to build a community of like-minded people and to contact people whom you want to relate to in some way. Anonymity defeats this social building and relation process.
There are still several places where it's not 'politically correct' to be known as a reader of/poster to groups like soc.motss, alt.sex.bondage, or other "controversial" groups. People may still want the sense of community that they can get from participating, while wanting to avoid the enforcement of PC-ness, possibly at the end of a baseball bat. Famous/infamous people may also want to participate in the online world without being swamped by "fan mail" - I suspect it'd be virtually impossible for, say, William Gibson to post to Usenet without being overrun by zillions of letters. I believe that Steve Wozniak (post-Apple) attended college under an assumed name for similar reasons.
A counter-response to this might be to say that we want to put privacy in, not anonymity. But again, I wonder about this. If I want my message to be read only by a certain list of people, why am I posting to a newsgroup instead of to a mailing list?
Distributing "secret" information widely, in an encrypted form, can frustrate traffic analysis - if I suspect that X is doing something nefarious, I could look through sendmail logs (or whatever) to see who she's talking to, and create a list of suspects. However, if X posts her secrets to the net - in an encrypted format - and those secrets are dispersed to the world, I can't draw any conclusions about anyone who happens to receive that encrypted message in their alt.test newsfeed. There's also no chance that anything peculiar will be showing up in postmaster mailboxes because of bounced mail; it's also a much easier way to talk to 200 people at once. (Assuming that it's meaningful to talk about sharing a 'secret' with 200 people .. :)
There's no point in privatizing the substrate, since anyone can get a client that will decrypt at the far end.
In sum, I guess I'm somewhat baffled at why one would want to use anonymity and/or privacy enhancement technology on one's news postings.
Generally, to (a) say/do something controversial, and avoid retribution; (b) for an [in]famous person to say/do something mundane; or (c) to make anonymity/pseudonymity not seem so peculiar, so instances of (a) and (b) won't stick out like sore thumbs. -- Greg Broiles greg@goldenbear.com Baked, not fried.