I tend to cloak myself in layers of anonymity in my professional online life. Mailing lists are not an exception. In fact, I try my best to participant on mailing lists in a way that does not disclose the company I work for, for various reasons (whether I stick to my other name or move back to LonerVamp, I’m still debating). I see other people do the same, and sometimes they use some wacky (and creative) psuedonyms that harken back to hacker days of old when handles were used more often than real names. They also typically come from email account at Gmail, Hotmail, or Yahoo.
To anyone who uses such accounts, be aware that how you use them may determine just how anonymous you remain. Using the webmail interface for each account is pretty secure when it comes to what the mailing list can see. However, if you do your email on a mail client and then POP3/SMTP up to the service, you may be revealing your home IP address in the mail headers. I am not sure if Gmail reveals this information, but I do know Hotmail reveals this. I encourage people to test such functionality well in advance of blindly trusting your security and anonymity.
Or, if the mailing list supports it, submit your replies via a web form. I know SecurityFocus has web-based submissions to its mailing lists if you so prefer. I actually prefer that method.