[babarock]

something about how you are the best person in the world to lead its execution

Completely agree. From this point of view, people are not investing in your "idea" as much as in your person. There's real value to be had here. I believe that more than anything else, people believed in Bill Gates more than they believed in any idea he ever had. I'm not an authority on the matter, but it seems clear to me that IBM made Microsoft, and they did so because of how their meeting with Gates went, not just because "a BASIC interpreter would be the future".

I'll add that since your value is tied to the person it is not easily "stealable". It becomes vital to get a prototype up and running as fast as possible. You need to show investors/cofounder/contractors/... what you have in mind. Describing with words won't do your idea justice, a prototype would add a lot of credibility to it.