To my mind and my experience unfortunately, if you have a co-founder who is doing only business without any other contribution (e.g. money) and he has same equity of your company as you then he is ripping you off. Better go to YC and give them 5-10% and access their network if you need a what u call program manager...
the reason you decide to start-up, is that although you don't know everything, it means you already know or u are willing to use other skills too and/or learn the rest (including those you are reffering to) , in order to encompass more characteristics --enough to take the risk to become a founder. Otherwise using one skill (e.g. programmer) should get you a job somewhere.
an non-YC example with female co-founder I am aware of is Emily Boyd of www.rememberthemilk.com
If you mean, the business guy can't read code, doesn't know how interfaces should look and can't visualise the direction of the product i guess you are right. But, strangely business guys are needed to get users and thats pretty hard - even if you are myspace or bebo. Bottom line - doesn't matter how great your tech is - someone who gets business makes or breaks your product.
The problem is that in the beggining there is not a product to push! And if there is and is launched even with some minor features showcasing the idea, then you'll receive feedback from the users, so you get this help from your users. This means, that having more features to produce you do need someone who is technically capable while the product/service is maturing.
Now if there is a product/service and that product needs someone to find clients that will pay for, and not relying in word of mouth, like most low budjet web start-ups do, then ok, you need someone who will help you with this, but does it really worth it giving up equity equal to yours?
For me, no because I believe that if its your idea (refering to 1 or more people), then you know it better. So, being the soul you can pursue becoming capable to talk about it and make others even invest in it.