In my own experience, this can work well in a small group with engaged students. I had an excellent optics class where we would try to derive a known result as a group: the professor would explain the experiment, draw a picture, and then ask us to help. If we got him going, he would take a few steps, then ask again. Now, I remember next to nothing of equations for optics, but I have a very good idea of how to go about figuring out the outcomes for various experiments theoretically.

On the other hand, I've had professors stop referring to notes partway through a derivation or proof, get dreadfully confused, and simply frustrate themselves and their students. So this may be an all-or-nothing: for a given day or proof or class, either do a group derivation or present the material on a platter.

I will say that I also had a high school English teacher who would use the wrong word or give a ridiculous interpretation in the hopes that a student would correct him and learn to not always trust authority. I liked the theory, but in practice it meant that the attentive students had to do work that was frequently repetitive and irritating, such as correcting word choice or grammar (as these were students who were already thinking) while those who could learn most from such a lesson never noticed it.