Watching you watching them
At the beginniing of December, Netflix tweeted "To the 53 people who've watched A Christmas Prince every day for the past 18 days: Who hurt you?" This was obviously supposed to just be a humourous comment, and many people took it at such. However (somewhat inevitably), there was also a significant amount of protest regarding the privacy implications of this tweet. There was considerable surprise that Netflix gathered user data like this.
Are these people right to be aggrieved? In short, no. Ignoring the fact that this sort of data collection is covered in the Netflix Terms and Conditions that they will have agreed to before using the service, even a moment's thought about how the service works should indicate that every single interaction you make with the site is being logged. When you log in as an existing user, you are presented with a list of shows you're in the middle of, including those you've stopped halfway through. It also presents a personalised list of other shows and films that it thinks you will like based on what you've watched in the past. This will be based on comparing your viewing habits with others on the service. To be able to do this, the alogrithms that do this need to be aware of all this data that has been gathered so that the comparisons can be drawn.
This sort of analysis tends to be run on anonymised data. This means that, in the case of the contentious tweet, while their reporting tools indicated that 53 people watched that film for 18 days straight, they wouldn't be able to tell exactly which 53 people did this. While this particular example was played for laughs, as you can imagine, this sort of data collection is essential to be able to work out what films and shows they should be putting on to the service. How many people that started watching a series actually finished it? Is there a certain point in the series that caused a big drop off in viewers?
Tracking your outrage
The next step in these stories is then for many column inches to be filled covering the "outrage" (including this article, of course). The big irony here is that, much like Netflix, every single click on the websites running these stories is tracked and logged (again, including this one). They will know exactly how many people clicked on that article, how long they've spent reading it, whether they then visited other pages on the site, their geographical location, and even things like age and gender.
The same goes for every interaction on Twitter, Facebook et al about this. In complaining about Netflix user tracking, these people are just creating more data points for all the social media giants to then analyse for their own gain (and get eyes on screens looking at their ads).
We're all watching you
Pretty much every website you visit is constantly tracking your movements. Especially those that are trying to sell you something. This isn't necessarily restricted to the site itself either. If you have ever noticed that an advert follows you round the internet, this is likely to be due to Google's remarketing tools. This allows advertisers to pay to put a snippet of code on your computer once you search for something and visit a website that sells that thing (or the manufacturer's website). Once this is set, Google's code on other websites then checks for this and shows you an ad for the thing you've just searched for, knowing that you're probably interested in it.
It's not just your online movements that are tracked either. Unless you've disabled it, your physical location is constantly being broadcast and logged by (probably) Google or Apple via your mobile. Google "accidentally" grabbed all the wifi network names round the UK a few years back when they sent their Street View cars round. Companies like Uber know a huge amount about your routine if you use them regularly.
So, in brief, if it is possible for company to know something about you, they will almost certainly have systems in place to log these things. There is a constant push to increase the amount of data that is logged so that these services can be increasingly individually tailored.
Should I care?
So does any of this actually matter? It's obvious that the current consensus is "no", as there are no signs that people have any intention on stopping their use of these services. People seem to have just accepted that this is the cost of using them, and probably think about it very rarely until it is thrust in their faces by stories like the Netflix one above.
For the most part, this data gathering is innocuous, or at least not personally harmful. The intention behind gathering these stats is almost always in an effort to improve the service that they provide.
However, it is always useful to think about what someone with nefarious intent could do with any data you are either intentionally or unintentionally supplying to a service. What if this data leaked - either hacked or via a rogue employee? Google log every single search you perform by default. This information exists on a server somewhere, and is therefore technically accessible by others. What if this information was made public? While opting out of all of this is often time-consuming, or impossible in some cases, it's always worth always having this possibility at the back of your mind as you browse around the internet. You may even want to consider switching a service like DuckDuckGo for searching, which doesn't track what you do.