I've done it twice. The first girl said yes, but then rescinded less than a week later once she began to see how I really was socially. Second girl flat out rejected me. And there have been a few other times where I've made it known I was interested through my body language and mannerisms, but they failed to reciprocate any interest.
I wish that number was higher but you kind of have to build your way up to asking a person out. You can't just approach some random girl on the street and ask her out. Ok, technically you can, but I'm not that smooth.
I haven't really ever gotten past that "ice breaker" stage with very many girls to reach the point of asking them out.