Revison 1
Function that you can use to extract the ID from YouTube links that
look like this:

http://www.youtube.com/watch?v=Fv2aS8YtpmU
http://www.youtube.com/vi/Fv2aS8YtpmU
http://www.youtube.com/?v=Fv2aS8YtpmU

and you can extract this "Fv2aS8YtpmU" so you can use it to get thumbnails that look like : http://img.youtube.com/vi/[videoid]/default.jpg