[scobar]

Have you directly expressed that you're looking for a co-founder to your prospects? Do you have a clearly defined mission for your business? If so, and you've told the prospects about your mission, their reactions should provide some insight into which are excited to work toward that goal with you.

I know that while I worked with digital goods, I was very intrigued by and pursued some challenges for fun when they weren't the best way to increase my income. The developers who are curiously attracted to the challenges you seek to overcome may be better than a less-interested but better programmer.