Maintaining [a professorial] image means drawing a line between your professional persona and your personal life.
Most law-prof bloggers seem content to put their blogs largely or mostly on the professional side of that line. While they don't always blog about law, they seem to refrain from saying stuff that would be inappropriate in a conversation with a student in their offices. Folks like Professor Bainbridge, or the Volokh Conspiracy, or Althouse, or Conglomerate maintain an informal, yet not-unprofessional tone. To varying degrees they trade on their academic affiliations, and would have relatively little ground for complaint if, for example, their law schools posted something about their blogs on the law school web sites.
Oscar wants to be free to use naughty words and otherwise break out of the professorial mode. But my experience is that even though students know who I am and can and do read this blog, they seem to accept this as a separate mode of mine and don't use it as a basis for talking to me in a newly confidential way. In the law school, the student-professor relationship is very well established. It really doesn't break down, even when students read your personal journal.
Of course, there are things I won't say here, but these are things I wouldn't say even if I used a keyboard name. I would never insult or demean or deliberately hurt the feelings of students. I wouldn't casually knock my law school (though there are some considered criticisms I would be willing to make). I wouldn't hurt my family or acquaintances or even reveal much of anything about them (without permission). So there aren't really any significant ways using my own name limits me. Like Oscar, I care immensely about freedom as I do this blogging. But I also want to be aware of myself as an identifiable person, responsible for what I say (which is true whether you use a pseudonym or not). And I don't mind getting personal credit for anything good I might happen to say. Also, I kind of like being a public persona.
UPDATE: I don't know but is a blog with an important good reason for remaining anonymous: to protect children. Here, the authors want to be able to write about -- among other things -- parenting children with Aspergers syndrome.