Tim Cook's email is widely available because of people other than Tim Cook posting it without asking permission, much like Mr Zenkel. I could guess all the other NBC executive emails too. Since emails usually bounce when incorrectly addressed it's very easy to get the format for any company. The more important information in the Tweet was that this was the specific executive to contact. I might have tried [email protected] because I didn't know any better.

If I was an executive and someone publicized my [email protected] email address I would not be upset in the least. I'd be more worried about the reason I was getting heckled--my job performance.