I thought the Joe BagODonuts was a good idea and agree that having a stealth student is a bad one. In the past, I've used a fake student (Wile E. Coyote or the like) for testing purposes when designing a course. Never occurred to me to have the fake student continue on and take the course.
It is interesting that students will interact differently with an online student persona than with an online faculty persona, even when both of those are fronts for the professor.
I've taught on line for five years or so and face to face for twenty. In both cases, I'm conscious of constructing a teaching persona which is different from "me." In the on line world, it feels more like I'm creating that persona from scratch, where in the face to face world it's pretty much me, but with cleaner language and a more professional and focused interaction style.
Once, I had the experience of being a fake student in a face to face class of my own. In September and October, I grew a long beard and didn't cut my hair. Halloween came and for my costume I shaved off the beard, got a short haircut, dressed in student clothes, and joined a 'panel of former students' who were in on the joke. The panel trooped into my undergrad class and fielded questions about the final project. At the previous class meeting, I had told my students that I would be out of town on the 31st and that the panel would run the class. None of my undergrads recognized me and the panel was peppered with questions, some of which were of the 'Is he a hard grader?' variety. See
http://www.basssax.com/images/JonBass.jpg v
http://people.emich.edu/jmargerum/images/jontux.jpg for an approximation of the difference. I only kept the charade up for five minutes, but it was fascinating. I broke character when it was clear that not to do so would be a violation of trust.
Back to the main point: I can see where it would be useful as an on line professor to develop a student persona and a professor persona. Having the student persona, for me, would be as useful from a 'voice' standpoint as it would be from the standpoint of how students would react. Both voice and reaction would be useful. That said, I would never obscure the true identity of the fake student. I agree with those quoted in the column that to do so would be a major ethical breach.
Jon