I am currently undertaking my PhD in Artificial Intelligence + publishing and thought I would share my thoughts and experiences.
Academic writing is generally a pursuit to contribute to the body of knowledge. Academics in general, publish to contribute to this public domain of knowledge. Universities tend to have their own Intellectual property offices which protect the interests of the research, but would never allow for a researcher to publish detail that could jepordise the universities intellectual property. This can take the form of patents and trade secrets.
If the knowledge is in the public domain and not protected in anyway, then people are free to do what they want. Think about this though. Research is never done, and these contributions tend to be very narrow contributions that are hard to protect. Most PhDs I know are carrying on the work from others around the world they have never met, basing their entire project from the public domain of knowledge.
Also, I had someone implement the algorithms I described in a paper and I was very flattered, not offended or angry. I find academics have different incentives to business people. If you email the first author, they might even give you all of their code. Many researchers in my field are happy to show off their work and see it in practice as it looks great on the CV.