facebook's failed experiment
They could have gone about that so much better. A simple, hey we're conducting an experiement for our newsfeeds, would you like to join in? spam message where people could have opted in like a beta test would have taken care of any ethical and legality issues. (People must be told not only they are being experimented with but what kind of experiments are being done.)
Companies have to remember that doing things without their customers knowledge is never going to get them to like your product better. Never.
If Facebook were to run an experiment (you know with all the ethical and legal checklists involved checked off), what would want them to run?