First off, to whomever ever said males 18-35 are MTV's target demographic, I'd have to disagree. I'd say both genders, 14-18 are the target demographics, but that's just me.
Secondly, the whole concept of MTV, whether they knew it or not, was doomed to failure from the start. It's a testament to their staff that MTV still remains on television today.
See, the whole thing with music is that it was, and still is, portable. Tapes had come out relatively recently, and walkmans were the big thing. Mobility was/is a driving force in our culture, both here in the US and in many places across the globe. Videos were neat things to create a buzz about a song, but couldn't be sold on cassettes, and couldn't be viewed on the road. As technology progressed, we got CD players, which still lacked any sort of video output. By this time, the music industry had realized that making videos was an exercise in throwing away money, basically. The future of music was not in video, nor would it make any sense for it to be - it's an audial medium. The exposure that a band got from a video contributed very little to it's sales, nor did selling the video to MTV make much moeny at all. The internet and MP3 basically sealed the deal, making music extremely portable and providing an easier way to create buzz for a product.
Now, the future of video IMO rests on the very technologies that helped kill it dead - the internet and MP3 players. One of the ways available for the music industry to develop is exploitation of the internet. To this end, why not make videos and sell them online? Or include them as extras on the CDs from the store? Sure, you're going to have a percentage of piracy; piracy is an unfortunate side effect of the internet, and one that is here to stay. However, I think they'll find that fans are very willing to support bands they like and this is one way to do it.