IS IT Possible for admins and moderators to see who views videos within their site?

Yes it it possible, it is called a log file, everything you do is logged or recorded in vivid detail depending on the budget of the website you visit, Most websites have a log that is used to track visitors, Google uses it, yahoo uses it and the government uses it on their website. I run multipliable servers and websites and i use logs to track errors and problems, but if you wanted to you could track more than that, like the web browser your using, your ip address, your location, the operating system of your computer, and more. If you don't want someone to see something than don't do it or visit it.