One of the values of VCs and networks and experts is that they can tell you how other companies in your space have failed (running out of money, founder breakups, "people won't pay for it", "it really needs X but X doesn't scale", etc.).
If you watch the start-up space for long enough you start seeing multiple teams with the "same idea" but only a handful succeed at it; even at small a scale as university incubators.
Here's another one: what is an idea? Typically it is a sentence expressing a business proposition, or the essential functioning of a technology. But is it the same "idea" no matter who utters it? I think it's pretty clear that an idea is actually short-hand for a 'space of experience' held by the person saying it. In this sense, it's actually not possible to "steal" an idea, because ideas are linked to the people who have them, and because were someone to try, they would find that they can steal the sentence that refers to the actual idea, but lack the perspective to unlock the true meaning.
Either way, this is a meme in the startup industry, and very true in my experience. Do not fixate on ideas: nobody can steal them and/or they are not important in the first place.
The concept to further research is execution vs ideas: https://www.google.com/search?q=execution+not+ideas
The reason there's no market is because it takes an idea and a person who can execute -- knowledge, skills, connections, experience, etc. Ideas aren't separable from people in a way that would make a market possible.
Most markets are for items there are many of. There are lots of apples, people see friends enjoying them, people buy one, like it, buy another, a price is established. Key facts: you get to buy it more than once, more than one person gets to buy it, you can tell in advance it is worth something. Take too many of those away, and the market goes away.
An idea (for a venture) is: unique (a close variant missing a key part has completely different value), you would not pay for it twice, and selling it to multiple people diminishes its value. Why would you think the value of an idea would be well captured in a market?
You do realize a market is just one mechanism for expressing value, right? or is air value-less?
Obviously it depends a bit on the details but if you think of the big hits, saying say Alta Vista is crap let's build a better search engine or Myspace is crap let's build a better one of those wasn't worth much for the basic ideas because hundreds of people no doubt thought that. Now the detailed algorithms may have been worth something. But it's mostly in the actually building the better thing that counts.
I guess knowing which ideas are good would be valuable. If someone had said you'd make a fortune doing myspace with real names and no flashing nonsense that would have been useful but just having a list of a 1000 ideas with no testing is probably not worth much.
Can you provide the numbers pls?