Certainly with any generality, there's exceptions. But if you are a guy with an idea and don't have the ability to build it, you're unlikely to be satisfied with the outcome of hiring a freelancer.

Freelancers are not employees. They're not attached to the business on a full time basis, and while they may get excited by the business and be happy to be working with the entrepreneur, in the end they are mercenaries.

Further, when the project is over and they walk away, the knowledge behind your product and technology walks away with them. This is true of employees as well to some extent, but at least with employees there's an expectation that they will be involved for a long term. For them it's not just another contract.

Contractors can be used to augment your development staff, but should never be your entire development staff.

Sure, you CAN have a success with a product built by freelancers (Digg is an example of this) but it is very, very rare.