What everybody's talking about are metrics. Anonymous usage metrics. And trust me, as a user and programmer I know of no company that doesn't collect metrics like that. It's totally common.
Between, as far as I know, from the next update "creators" (this or next month) you can actually turn them off too.
Oh wait, it has been documented by third parties.
Win10 has a whitelist in the signed 64bit kernel mode network driver, so you can't stop it except by putting a hardware firewall in front of your Win10 box - good luck with your Win10 notebook.
If an app sends home metrics, it can be stopped with a software firewall. If you can't trust your operating system any more, it's a whole different ballpark.
Adware and spyware companies with their unwanted toolbars and what not got problems with the US law since 2004. Win10 is an adware and spyware per definition, see news article of this HN thread.
Furthermore, even if the current system is OK, this might change at any time without prior notice due to a pushed update.
Finally, others doing it, too, doesn't make it any less wrong.