Ryan Lowe makes a great point in the course of noticing that the Eclipse foundation is trying to hire an Eclipse evangelist:

Not only would a project give the evangelist invaluable experience with the Eclipse platform and something to blog about but it would also help them sympathize with developers, the exact people they are evangelizing to. It would put the evangelist on equal footing with other developers -- the evangelist wouldn't just be some suit telling me to use a platform because of x,y and z.

Exactly. An evangelist who isn't living on the platform just isn't credible - how can he (or she) possibly empathize with real users and their problems? I can tell you from experience - I spent many years as a sales engineer, doing demos, writing examples - and while it was useful, it never really gave me the same experience that our customers have. Over the last few years as the Product Manager, I've written (and deployed) some real applications - both client and server. It's given me a much better perspective on the highs and lows of the Cincom Smalltalk platform - one I don't think I could have acquired any other way.