I work in the corporate world, I have detailed confidential discussions about technical details of upcoming products and contract details. The first thing we do in those situations is we all sign NDAs. The idea that you'd do a presentation to a hundred people and expect that information to stay confidential without specifically informing them is just absurd. Which is part of the reason Jobs just screwed him around rather than doing what you're meant to do - get the person to sign an NDA and then sue them if they break it.