I have experienced similar success but on a smaller scale.
When I just started out on marketing my site I thought I'd head over and all-in-all I've answered probably just more than a handful of questions and not even all of them have links to my pages, yet those questions with my answers were the first to appear on Google's listings for my keywords and the amount of traffic I've received from those few links is quite promising.
I've been thinking of dedicating time to that on a regular basis, but haven't had the encouragement, perhaps now I will do it
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Thanks for the info!