To me, it's all a matter of what you would call "mainstream". It could mean differnt things to different people. Look at all the bands that have had quite a bit of popularity from their videos being shown on the new Headbanger's Ball. True, a lot of what they play is not "metal" to some ears (thats an entire differnt issue I'm not going to get into) but more "aggressive" styles of music have found much more exposure because of it. Then again, that's MTV2. If you consider mainstream to be MTV, then no, I don't ever see extreame metal being played on there. I call that channel mainstream, and when I think of it in that sense, I think of domination by other forms of music, such as rap and pop. Of course, there are types of music that have exposure outside of MTV. Hell, I know of 4 channels that are dedicated to country music. Such is the case with extreme metal in ways. It has internet radio stations decicated to it, various 'zines, ect... But to me, in the end, it dosent really matter, because no matter how popular certin bands get, or no matter how much exposure the music has, it's here to stay, and I will always be a listener.