Recording provides terrific benefits but requires a demonstrator to "play to the camera" and a committment from the group to the to be respectful of the camera. If the camera is unable to see it or hear it,you won't either on the DVD. By the same token, anything unwanted which passes before the lens or is picked up by the microphone is captured and can pose a problem during editing.

As Dan said, "Many groups do this." UMBA, for one, offers hundreds of titles,very reasonably priced($7 for first and $5 each additional) Prompt shipping is included in the price. (One caveat: their early efforts are frustrating, but they now offer first rate educational recordings.
OBG and AFC also record demonstrations. Another blacksmithing guild in Colorado offers somewhat costly recordings.

BTW, Check out UMBAs RD123 & RD130. It is an ENTIRE CLASS as taught by Steve Williamson at JCCFS.
One is in our library,sent by Roger Degener when he edited my originals in 2006. You can get your own copy for just $12