As we may ask and answer various questions on online forums or stack exchange regarding teaching, research, publishing etc; it may reveal our lack of knowledge on any basic topic. This might hurt us in the future as an already established academician. So, should we participate in those online forums or stack exchange sites under pseudo-names to remain anonymous?
I post under my real name, mostly because I started out by doing so on MathOverflow (where this is encouraged, and which I see as an extension of my public mathematical career). I have a general sense that this adds to the professional atmosphere of this site.
I'm not too worried about damaging my career by posting a question or an answer that looks stupid or "reveals my lack of knowledge". I have no doubt I've already done that a few times, but I have enough trust in the academic community to believe that a reader will understand that I write in good faith and my goal is to learn and/or help. I also trust that any reader will remember that they've had "stupid" questions or opinions of their own, and avoid judging me too harshly.
However, I do take care to keep my posts professional, remembering that I'm speaking publicly. Among other things:
I try to maintain a calm, courteous and measured tone in my writing. I take extra time to make sure that what I post is reasonably well written, and hopefully not subject to misinterpretation.
I will share my own experiences where they relate generally to academic life. I won't share details that implicate other people who could be identified, reveal confidential or non-public information, or expose details about my institution's internal politics. I won't post rumors or hearsay, or incidents that happened to other people (unless they're already public knowledge). I won't share experiences that are overly personal.
I'll share my personal opinions or advice on academic matters, particular where I think my views are likely to be representative of the academic community as a whole, or a significant segment thereof. If I have unusual personal opinions on a particular issue, especially if I think they're likely to be controversial, I'll probably keep them to myself; partly out of self protection, but mostly because I don't think people who ask questions here are looking for answers from the lunatic fringe.
Contrary to ElCid's answer, I have no expectation of impressing anyone or building my academic reputation with my posts here.
If I have a question or answer of a sensitive nature, I would post it anonymously (using Tor or something similar to hide my IP address if I were particularly concerned).
I understand that other participants may prefer, for their own reasons, to participate under pseudonyms. I fully respect their decisions.