I have a personal bias against martial arts DVDs - not videoing in general, but the idea that you can learn something just from watching it on a monitor.
Many will disagree perhaps, but that has been my experience.
Of course, if you already KNOW physically what you are doing, and just need a reminder as to some of the technical parts, alignment etc of what you are practicing, then they are very helpful as an 'external memory' device, holding information until it has been fully integrated through practice.
The dilemma comes when folks start asking for material to work on remotely that have zero to very little idea of what they are doing.
A common question I get asked is about the availability of training videos of Sonny's material, and my answer has up to now, been no, sorry, not at this time.
Part of me really wants to keep it this way. I believe you learn to 'dance' best with a partner, reacting and moving because they move, and learn particularly well if you have a skilled partner that can lead you and set up 'questions' that you have to find the answers to.
It's pertinent, practical, and in my experience, a highly efficient training method, with hopefully, little 'un-learning' to be done on the way to understanding the art.
The other part of me thinks, sure, why not have some material that is available to practice remotely? After all, the pendulum and all it's variations are perfectly possible to practice solo, especially if you can hang a ball or some kind of weight on a string, from the ceiling to move with ....
But then I remember how errors creep in with no feedback, especially for those with poor proprioception, and am leery to encourage folks to imprint these errors through repetition, if these problems will only have to be erased later. The human mind has a high capacity for delusion and has a particularly hard time being objective, even with physical movement .... So ...
To video, or not to video ...?
Is not videoing preserving the integrity of the method? Or just being a control freak?
Is distributing a learning video sharing knowledge? Or just throwing out meaningless information?