Oh baby, there she is.

That's because the closing bracket got attached to the address. Delete it and all will be well.

Whoa, was that a real example? Because it looks like that username is already invalid.

But then we have to only have official links... which is not very likely

If we copy the video of the official page of a singer (for example: http://www.youtube.com/user/shakiraVEVO) it's rather impossible that will be deleted

YouTube videos get deleted all the time for copyright reasons, you will have lots of dead links after a while. You could also make a button that searches youtube for that title.

Well in many contributions the IMDB link is skipped too, anyway
Maybe what I should do is that if the user does not provide IMDB link is to make appear an extra field which would become the 1st comment of the movie page, asking the user to provide youtube link if it is a videoclip, or some comments/links if it is a documentary/movie not listed on IMDB (and force him to put something in that comment field)

Ok, anyway the idea of the youtube link field is not bad: noone now, put the link of the video in the comments.... at least, with a field that appears when you choose "music video" the users that provides a lot of music video can add the YT link on the site

The movie number is an integer number field so we can't store a youtube link (contains letters), but I could add a separate youtube field. Though that in such case we can also just post the link in the comments.
The reason of the IMDB number/link is that we need to have a number for each movie, so instead of taking "random" numbers (like what is done for movies/clips which do not have IMDB number) I thought it was good to use the same numbering as IMDB to be sure to not list twice the same movie (this already happened with movie clips) and to easily build the IMCDB link from the IMDB link.

I don't know if someone had already proposed this thing, but if the music videos are not on IMDb why we don't add in the IMDb number field the code of the youtube video? I mean the code after "v=" in the address... This for example "6WKRfgT3Tv4". I don't know if the system is modifiable for recognize the difference between a imdb code and a YT one...

Then we add this picture instead of the imdb logo:



(resized obviously ;))