from a theoretical perspective EADG mx makes sense. That is always how I saw it, and i always wondered what all the fuss was about (granted, i am not much more than a hack).
i have only just recently begun to see jeremyr's perspective. if i were to try to summarize (my possibly incorrect) understanding, i would say that it's a more "pragmatic" approach: that since a song is always a sequence of chords, at minimum, your hand is positioned to play the chord tones. with the chord root underneath one of your fretting fingers. at that point, you know the "compatible" modes to that chord + harmony AT THAT POSITION and you can go off from there. if the compatible mode (to the chord) is in a different key center than the rest of the song, no big deal, you have temporarily modulated the song to a different key center, and it will sound more like modal harmony rather than diatonic harmony. whether this actually sounds ok is dependent on whether your band mates are also on the same page...or are leaving the sonic landscape harmonically ambiguous to allow you to go in either direction.
jeremyr, am i getting there?