Captain Craig wrote:
Coulson's death was easy for Whedon to add, if not necessary. Frankly it's a Whedon thing, no one stays happy forever. He's killed plenty of characters that always felt necessary.
Killing characters is "a Whedon thing," yes, but not in this case; the decision to kill off Coulson was made before Whedon even came aboard. I think I even read somewhere that he resisted doing it because he knew people would go, "Oh, there Whedon goes killing off our favorites again."