I attempted to start businesses with a few friends of this type when I was younger.
The result was mostly the same: I would spend weeks/months working on the product/idea, idea guy would either get bored because they are just sitting there waiting for the launch and move onto something new or attempt to become my defacto manager.
Some people like the idea of running a business and seem to think it only involves telling other people what to do and waiting for results (as if that's the hardest part).
The other concern is that what happens to this person in the next phase of the business?
Many ideas people will realize they don't have the skills and will try to push for ideas that aren't necessarily better, but that they can attach their name to...causing havoc.
Ideas are easy. I have tons of good ideas and the skills to execute. Now, I will only consider parterning with someone if they have money to invest or a relevant business network+some other skill.