This question already has an answer here:
I found this one on UserVoice, and I thought it was fitting to bring it up here for further discussion.
"Stack Overflow already works with Mobile Safari, but the experience is far from optimum. I believe an iPhone-optimized version (or maybe even a native client) would be perfect. I can help with either."
I personally think a some kind of mobile version of Stack Overflow would be great for using as a reference, but using it to ask questions would probably get cumbersome if you had to type up a long question with full description. However, using it to look up an answer when you're away from your desk would be awesome.
But, why not just use the regular Stack Overflow? Well, we all know that the small, touch screens get cumbersome to use when navigating websites built for desktops.