The phrase orginated as "the proof of the pudding is in the eating", which makes a great deal more sense. What intrigues me is the question that BrandWeek poses to CMOs in their Best and Worst Marketing Ideas for 2006.
If you're dating then what are the things you do?
How do you get from dating to engagement? There are no guarantees that the other person won’t choose someone else. However, you may have a good sense of what are the things that you do that will keep the interest high.
Would you ask your date for permission to call them or send them an email? Would you give them reason to see you again by providing a memorable experience for them? What is this relationship worth to you? Are you willing to give your date attention and care?
Reality is socially constructed. When you give people a platform to stand on -- products and services worth talking about -- and a megaphone to use -- are those free services they can spread? --, they will become your advocates. And while you're at it, do you treat different people differently online?
When you do all those things well you will get your proof: your sales will grow.