So, Facebook has been in the dock after publishing details of a supposedly sinister experiment it oversaw several years ago. It involved monitoring the moods of around 700,000 users based on their posts. The research also established that it was possible to affect those moods by posting positive or negative content in the users' news feeds.
The reaction has been highly negative, with many people raising concerns about the implications for privacy online. Whether or not you think they are right, they could probably do with an update on what has been happening online these past few years.
We are entering into an era where data is king, where our every move, our every emotion and every contact can be tracked. With the increasing analysis of social media activity, there is often very little that we do that can be hidden from the organisations we interact with online.
So long as an online company can drop a cookie onto our machine, it can track our behaviour online. This now includes logging how we react to advertising material and especially what makes us click on the content. Increasingly they are learning our behaviour as a result.
The need to gain permission, in the same way that research teams require when they involve human participants, has been slowly eroding. It is coming to be seen as a natural extension of existing practices, where advertising content is focused on target groups.
Users often freely offer their data to the Internet, to be used in ways that, frequently, they would never expect. For example, a tweet on a local event will time-stamp where a person was at a given time. It may reveal information around their movements and even perhaps who they had contact with along the way.
One vital ingredient of following users' data is for advertising agencies to understand the emotions that lie behind messages posted online. Advertisers have always sought to mine the emotions of large populations as they respond to advertisements - this is arguably just an extension of it.
Making sense of people's emotions on social media brings new challenges. It might be fairly easy to make sense of a tweet that says: "I am so happy that the sun is shining today :)"
But just by placing a different emoticon on it, you can change the sentiment: "I am so happy that the sun is shining today ;)"
And then you can change it completely if you add the dreaded exclamation mark: "I am so happy that the sun is shining today!"