When it comes to performers wanting to have a clip withdrawn, for various reasons, that's fair enough. So far as other owners of copyright exercising their power over their property to prevent a performance being heard, against the wishes of the person who created it, it's a case in which the old slogan "property is theft" does indeed seem appropriate.

YouTube is of course going to comply with the demands in such cases, because they are vulnerable to legal penalties if they don't.
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If people want to download YouTube clips, it is very simple. All you need to do is find the tmp file in the cache of your browser, copy it into a separate folder somewhere, and replace the tmp by flv (just type it in) and maybe change the name to something more recognisable while you are about it), and then it will open with various free programme. One that seems to work very well is JW FLV MEDIA PLAYER

Finding the tmp file in among all the others can be tricky, and it's easier if you have made a point of emptying the cache first. Perhaps have a browser set up that you just use for this purpose - Opera does well, because it's very easy to clear its cache by opening up "delete private data" under Tools. (And to get to the Opera cache on my PC it's My Computer/Documents and Settings/Application Data/Opera/Opera/profile/cache4.)