I think, like much in life, the answer isn't so clear cut. As some have already alluded to, there are factors to be considered. Two of the most important are 1)what's your background and 2)what's your goals? If your goal is to become proficient in self defense and/or fighting, AND you have no experience in either previously, then I think most would agree no, this wouldn't work. But let's change a variable...if you have experience (or already are training elsewhere) training "live", then it's a maybe. If you can integrate your virtual training into your live experience it may work. You may still be rusty on things like timing, position, etc. But your virtual training should offer SOME benefit. Now let's change another variable, your goal is not to fight and/or enhance your self defense skills, but rather are looking to get the other qualities of martial arts...exercise, physical skills (balance, awareness of body, etc.), mental simulation, etc. I'd say yes. Again, prior or current "live" training will make this much more productive. The closer you get to live training the more beneficial it will be. Does the virtual training allow questions? Do you submit videos for review/grading that get true feedback? Virtual is never going to be a substitute for live training, but that doesn't mean it won't have value. It depends on your situation and your goals. Incidentally I think we all would agree that you should direct yourself to what you want to do, regardless of the opinions of others.