Great article, and it confirms a few theories I had about online marketing research strategies.
I used to play a game on other forums where I would attempt to discern whether a particular poster was being a world class idiot because he wanted attention, or because he was mining data.
I'm sure most people on this site know this, but your personal information is valuable, and I don't just mean that for illegal activities.
After a month or two, if you keep seeing the same topic (with similar questions) coming back week after week after week, and from a new account each time, chances are good that it's one of the marketing researchers stirring the pot; looking for fresh hits.
Some of the others I've seen become regulars; rarely posting, but always slowly nudging the conversation towards a specific topic.
It seems like stalking? Well, it is to a large degree.
I recall one of the first lessons taught in my network security class: "True privacy doesn't exist on the internet. Whenever you go online, you're going public in some form or another. The more of yourself that you leave behind, the more the world can find out about you."
To drive the point home; any information you can google about yourself, is information that marketers can gather about you.