Some years ago the reference site for technical Q&A was expert-exchange.com it got to be a very good site until their owners decided they where not making enough money with ads and decided to establish a subscription service.
That meant that all the answers that people gave by that time where used to make money for the guys at Expert-exchange, they use the data I gave them free for their own benefit, and I (like other experts) saw no penny at all, not even appearing on web searches as the site was not accessible by crawlers.
This kind of issue will sure repeat, maybe with stackexchange or java.net, some folks will claim your hard won knowledge (as you know information is power) to be theirs using EULA’s and lawyers.
So when you publish information in public forums be sure someone is making a benefit at the cost of your bills, your light, your time, your experience and studies.
Many sites use your expert advice to make data mining and prevent you from making any money of your knowledge, and maybe knowledge is free, but your mortgage is not. So be sure not to share information you or others by your side can monetize in some sense, unless you don’t care about money at all, of course.