From my experience - likelihood of succeeding because you tell people and all the other variations of this are just hoopla.

You will succeed if

1. You have a market

2. You service that market better than most or better

3. You can do what you are doing for years at a length. And then keep doing it some more without even thinking about it.

Sure, the idea has to be semi-solid. I was referring to the part of "Get this thing done, now. Get it out there and in front of people. Then we'll see if they bite."

I agree with the last 3 things you said but I think there is value to publicly announcing your intentions. It shows commitment to the idea and the willingness to sacrifice your reputation for the idea (there is a cost to people knowing about your possible failure, and the cost of people you care about and respect of dismissing your idea).