Professional photo man uses a canon eos 1d and the mother of all flash guns, pointed at the ceiling so as not to bleach the subject..
He wasn't pointing it at the ceiling to avoid bleaching the subject. Theres two (2) reasons for it:
1) If you use a direct flash, the light bounces back off the chalk and you get big glowing spots in your picture.
2) The flashgun is a small light source and therefore produces very harsh shadows. Bouncing it off the ceiling means that you use the whole ceiling to light your photo and the light is even and smooth, with soft shadows. The only problem is that if the ceiling is coloured it can add a colur cast to your images, which has to be removed in post.