My show was the 7/3/77 (I think) show at MSG. they opened with "Animals" and as Roger sat on the stage with his acoustic, playing "Pigs on the Wing" somebody in the audience shot off an M-80. His reaction was over the top. After the yelling and cursing of the crowd, he came an inch from pulling the band off the stage.
I wasn't at the show about a week later in Toronto, during which he lured a fan to the front of the stage area and then spat on him.
These two incidents are supposedly the seeds that led to the isolationary, cynical and bitter themes that comprised "The Wall".
By the time "The final cut" was released, David and Roger were basically no longer speaking and Rick Wright was relegated to "session player".
Too bad...IMO they represented the pinnicle of the genre and their creativity from "Meddle" throught "The Wall" was unparalled, again IMO.