Ive refreshed some of my videos in the past to check and it doesnt count a second time.That's because YouTube does a lot of checking for views. I just tested it and added 4 views to a video. (And it takes a few seconds to update the viewpoint). Also over 300 views they do a lot of checking. Under 300 it's a lot more lenient.
Because it's not meaningful either way. Tracking all videos on youtube is still far from the complete picture. You yourself talked about facebook videos, and there are tons of other sources that also effectively take away views. It's impossible to get the complete picture and no matter what the numbers are meaningless without context. I personally prefer sticking to official uploads because you have a far better understanding of everything and can tell why a video is doing better or worse than expected.It really depends on what we are looking for though. If we are looking to find how many people hear about a game online, that's pretty darn impossible.
But unless there is some trend like MS being bigger on Facebook and Sony being bigger on YouTube, there is still some sort of trend that we can get from YouTube.
Look at NPD, they don't have access to every store and an exact count. But they can gleen a reasonable amount of information from what they have. There are similar analyses with Twitter and Google search engines that are done. They obviously dont give the full picture, as Bing and Yahoo are also search engines.
More information is better unless it's biased in some way for some reason, which it absolutely might be.