There are a number of things to watch out for with video cameras/camcorders. Firstly, you need to be able to use them properly, so some training for teacher and students is a good idea. The second danger to watch out for is that students don’t take the situation seriously enough and just fool around with the camera.
Lastly, we have to make sure that a student doesn't get stuck behind the camera – and therefore lose out on chances to practice English.