If you upload your video to Youtube and say 10 of the more popular video web sites and add a link to your site in each of the descriptions - does Google regard this content as duplicate content or link spamming? I guess it is the same as submitting the same article to multiple article directories. No penalty but not all the video/article sites will contribute Google juice?
I think a site can not get penalized for backlinks, as if google used to penalize sites for getting too many backliks, or backlinks from same video on different sites or from same article on different directories, then people will start to do all this for their competitors in order to get them penalized. The worst that can happen is that google will ignore such links, that is, you will get no credit for those links. You can get backlinks via submitting videos etc, but it is very much possible that google will only count few of them.
The most well indexed video site will a good points (of course and it might be Youtube). I think there's nothing wrong about this but only few will get much attention from Google.