Re: "tracks around 25,000..types of "event"..techies are also able to add new events"
And be aware it's not only Windows or Office. Today most developer tools offer libraries to add telemetry to applications, and not only Microsoft is abusing it. Obviously, whatever you do in a web application is easily tracked, bot more and more native applications, on mobiles or desktops, and even servers (and of course IoT), are instrumented to record and transmit telemetry. Some companies offer 'telemetry as a service' packages. We have to hope some highly visible investigations and frees will put a stop to this trend making it not legal.