The evil is in how you use the data. And of course, if you share the data with a third party (that includes if you use their services to collect or process the

The evil is in how you use the data. And of course, if you share the data with a third party (that includes if you use their services to collect or process the data), you should logically assume the worst. I would probably be okay to share all kinds of data with the websites I use, if I could reasonably trust that it will never be used to identify me personally. If you have a website, and you are curious whether your audience is mostly male or female, young or old, using computers or smartphones, I can understand the need, and would not object against my presence increasing some number in the database by one. Well, there is this problem that if you collect too many attributes about me, and if they are all connected together (as opposed to merely increasing a few independent counters), a sufficiently large collection can be used in the future to identify me uniquely, which is the part I object against. And I have no control about how you store the information, and it is reasonable for me to assume the worst. To make an analogy with the offline world, if you e.g. give a public lecture, you can see what kind of people are in the audience. And I would feel no desire to wear a mask for the purpose of hiding my age or gender or race or whatever from the lecturer. But I would object against someone taking my photo, using it to identify me, and writing the information of me attending given lecture on given day into some huge dossier about me, that he would later share with other shady people, so that they can all have my incredibly detailed biography (in case of Google, including also most of my private correspondence). That is definitely evil.