It also tells me straight away that the idea has never left the idea person's head. He hasn't talked with technical people to understand if it's feasible, he hasn't talked with potential customers to understand if his idea is attractive to them and if they're willing to pay for it, and he hasn't pitched to anyone for funding. In fact, he is probably guarding his idea so tightly because he knows that idea alone is all he has to contribute. I have drawers full of those kinds of ideas I could build, I don't need an idea person for that.
If all the idea person brings to the table are things I could do myself with a trivial effort, then they have no value at all. The real value comes from things that are difficult to achieve and take hard work. Like relationships with customers, deep understanding of what is the simplest possible technical solution that will satisfy those customer's needs, and the ability to bring in highly skilled employees, partners and funding.