Bronne, this was already addressed in the posts that can be found
here. It really comes down to choice, someone posting "hxxp://www.youtube.com" verses "youtube.com". There's really no right or wrong way to do it, some ways of doing it just make it easier than others. I'm sure over time more people will catch on and leave out the "hxxp://www" entirely.
There's nothing in the forum rules that says people cannot post direct links, to youtube videos or anything else. It's just becoming common practice because in the past we've had some people (from youtube, flickr and other sharing sites) find their way here from a direct link. They see their content posted on the forum and report it to be removed. Another problem with direct links is with youtube, the youtube member seeing where their video is being linked and either removing the video from youtube or making the video private.
Think of indirectly linking as a way for you to see that video, where otherwise if it was directly linked, it might not be there by the time you go to view it.
Slick