Maybe that is a little bit of the mark right now, but wouldn't that domain knowledge be a great opportunity for a non-tech co-founder to add value to a start-up? Just guessing, but there are a lot of domains out there that are quite diffcult to learn but that are also (or maybe because they are difficult to learn) ripe to be changed by software.

I could imagine the right match of domain knowledge and the capability to learn how to develop in a non-tech guy and programming skills and the capability to learn the domain in a tech guy would be rather powerfull combination. And pretty rare one, I guess. At least for me, the actual programming part is... difficult. ;-)

On another point, this applies pretty much things like lean or six sigma, too. Both are quite usefull (or can be, that depends!), but people tend to see them as domain by itself. In practice, and that's only my personal opinion, this comes out short. If you add this to existing expertiece in a certain domain, then it works!