Everything is near worthless if you can't market your product right. What would eBay be without the sellers or the buyers? Similarly, how did Yahoo Answers and AnswerBag successfully launch their question/answer sites? Without the proper distribution, it becomes the "dead zone" you speak of. However, the evidence is clearly there that these sites could work (Yahoo Answers, Answer Bag, StackOverflow, etc).
Now as far as this particular idea on selling experience, I would imagine the traffic and activity would start from the ones interested in selling the experience. The interests need to start with people with valuable experiences who may show interest in trying out the service to see just how profitable they could be by sharing their unique experience. Then this can spark interest in the "buyers" who may find the right experience/knowledge they were looking for.
If you get the right distribution, I believe it can overcome the challenge you speak of. The question I would ask you is: "If Google launched this service tomorrow, would you think they can make it successful?"
This said, I would agree that it would be a challenging start-up if you do not have the right plans/capability to scale up.