I have written 85 SO answers, yet I have never posted a question of my own on SO. Even so, I think SO has made me more productive, and that's counting all my time answering questions as wasted when in reality my time spent answering questions was certainly not completely wasted.

My primary reason for believing that SO has made a net positive impact on my productivity is that about half the time I google some programming problem, I end up on SO. I'm fortunate that most of my questions (or questions similar enough) have already been asked on SO.

I suspect I've read thousands if not tens of thousands of SO answers, and most of those answers were far more helpful than what I was able to find elsewhere.

I've often wondered why I've never asked a question myself. I think part of it is that I like searching/tinkering to find answers, and I hate waiting. I know it's not the best explanation because I know how quickly some SO questions can be answered.

I guess I should just be thankful there are plenty of other programmers more than willing to post SO questions.