There's casual Pirate Bay piracy, and then there's private torrent trackers: members-only clubs that share the best movie and TV rips among themselves. As you'd expect, they tend to be pretty hardcore about privacy, enough so that some groups are banning members from using Windows 10.
Windows 10 has had some issues with over-sharing information, from sending Wi-Fi passwords to your contacts, to recording usage data like typing a little over-zealously. The worst over-step comes in the services agreement, a document that covers the use of Windows services like Cortana, Skype, or Xbox Live.
"We may automatically check your version of the software and download software updates or configuration changes, including those that prevent you from accessing the Services, playing counterfeit games, or using unauthorised hardware peripheral devices."
If you read that with your tinfoil hat on, yes, you could probably conclude that Microsoft might be scanning your harddrive to look for a bootleg copy of Call of Duty. But it's more likely that the language is there to cover Xbox services, which do look for counterfeit games.
More importantly, there's no evidence that Microsoft is actually shipping details of your files and applications back to its servers for analysis. But all the facts in the world won't matter if everyone's so worked up about Microsoft stealing their information to actually use Windows.