People who have uploaded videos on YouTube know well that views are linked to the number of times a video is viewed "as is". This does not depend on the IP address or the specific pc, and even if the page is refreshed, this is still counted as a view. This simple views system, thus, takes into account only the access to the video without regard to the origin of the viewer; if he is the uploader or not and the number of times he has viewed it.
However, the catch here is that YouTube's views count stops at around 300 own views, increasing again if and only if the other viewers reach that number in which case the count will continue again.
As you can understand, when you encounter videos with staggering views, say in the realm of 20,000K, 50,000K etc. you can be sure that the views are significantly inflated. Fans of a video are likely to see that video tens of times, and more casual viewers a couple of times.
So, how many are the independent viewers?
The short answer is it depends.
Is the content of the video informative, of a technical or academic nature? Chances are most views are independent. Contrast this with music videos, videogames, sports highlights etc. Here, many people will bookmark the video and see it from time to time, show it to friends, share it in forums and in Facebook.
This is backed by the fact that the vast majority of top viewed YouTube videos have to do with music and humour.
Certainly, the actual independent views are a fraction of the nominal value in display. You can take this into account when intuitively estimating the real independent views of YouTube. Remember that independent views can be only smaller or equal to the view count. In reality, virtually all videos will have independent views less than the overall views.