@Frey and anyone who wants to know the meaning of "MAD" videos, here is an explanation by someone that is not me. It is quite informative and detailed:
Courtesy of @Rinneko: MAD stands for Music Anime Douga. Douga is Japanese for Video. It's synonymous.
Differences between MADs and Anime Music Videos:
An Anime music video (AMV) is typically defined as a fan-made video using Japanese animation, set to an audio source (typically a song). That same definition applies to many MADs. As stated earlier though, MADs consist of much more than this. There are audio and image MADs, and even MADs that are unrelated to anime.
The main difference between AMVs and MADs though, is the fact that MADs are more like parodies. Instead of clips from anime series, MAD videos use similar effects found in opening or ending sequences of anime. Those effects tend to be synchronized with the music. Furthermore, MADs do not necessarily have to be anime related, where as AMVs are implied to require anime.
Currently, MADs have been originating from Japanese sources. The MAD community designates itself to be in Japanese exclusive only. This may implies that anime based music video of non-Japanese origin are deemed as non-MADs. This of course varies since some people also categorise them as MADs as long as they are in japanese language.
TL;DR: The difference between MADs and AMVs is about the same as the difference between anime and cartoons.