I think its great when the 'non-technical' co-founder even knows their way around coding a little bit. Otherwise I find you have to explain every single thing to them and they don't have a solid grasp of the problem.
Getting to know your way around a language like Ruby isn't all that hard.
As a technical person, I run into people all day long that have 'big ideas' which are often mashups of existing sites, "Its like Facebook for FOO", and will never find a technical co-founder because they don't have any idea what the scope of the real problem is, or how to distill it down to something small, useful and graceful. Lots of ideas, but having an idea of implementation is great too.
Equally important, a technical co-founder must be able to explain complex technical issues in a way "regular people" can understand them. This is dramatically more difficult than it seems. In general, I think one of the true signs of well-rounded intelligence is being able to distill a complex idea into a readily understandable one. Think of pg, Salman Khan (Khan Academy), etc.
Getting to know your way around a language like Ruby isn't all that hard.
As a technical person, I run into people all day long that have 'big ideas' which are often mashups of existing sites, "Its like Facebook for FOO", and will never find a technical co-founder because they don't have any idea what the scope of the real problem is, or how to distill it down to something small, useful and graceful. Lots of ideas, but having an idea of implementation is great too.