I would be ok with very basic anonymised stats like used Operating System, CPU, GPU and so on because I would be interested in such stats myself and also in comparison with Steam. It could be as opt-in (disabled by default) or requested on first start. That would be a fair compromise.

Track me and I stop using GOG and go back to piracy.

I will not be tracked. I refuse to be tracked.
I will not take the mark.

No to game tracking of any form.

I honestly don't see a reason in having it made for us players to see. If anything, I think only GOG staff will ever find the need or use of such statistics. Heck, I'm sure they already have one implemented somewhere in the system they use.

I've found some games transmit some data to GOG, at least in enough to show achievements on your profile even without using Galaxy. More info here. I haven't really played any of my GOG games since, so I haven't really ran into it anymore.
https://www.gog.com/forum/general/achievements_without_galaxy

As Pheace said, it'll actually make GOG look even less popular. The more optional you make it (opt-in, etc), the less accurate it gets. And unless you require a compulsory Internet connection, things like recoding offline installers to make a "ping" to GOG servers every time the game starts also wouldn't work behind "block by default, allow by exception" / whitelist firewall rules (which also block in-game telemetry, eg, Unity Engine level).

I'm pretty sure Galaxy already has the capability to collect and send back Steam style telemetry (OS version, screen resolution, CPU, GPU, etc). They can already very easily tell how many Galaxy users are playing what, when for how long and almost certainly have the data you're suggesting. Perhaps the reason they don't make it public is that doing so only really benefits the most popular store, ie, releasing public stats that show 50x fewer people are playing the same game on GOG than Steam and that's not going to look good to a lot of games devs... (Example: Supraland was delisted from the store this week because it turned out that GOG made up just 1% of their sales when they compared store vs store stats). That's exactly the kind of data the store with the least sales doesn't want made public...

Don't use it and never will and this would be just another reason not too.

5 years later... necromancy is really on the rise currently... ;-)

It's a trend: remakes, remasters, reboots, ... digging up old threads and doing a Frankenstein on it.

Lol...

Thread remastered: The same thread with corrected spelling and grammar mistakes and new and improved formatting.
Thread remake: The same thread, but with less swear words and smoking and different (and more diverse) participants.
Thread reboot: The same thread by name, but going in a different direction with more harmless swear words and more diverse participants.
Thread Frankenstein: New thread out of copy-pasted bits from different, recently deceased threads.

See, very different... ;-)
And I could swear I have seen everything of that here on the forums except for the remaster. Spam bots actually do the Frankenstein thing to gather rep and appear as normal participants. Remake and reboot have happened when moderation had locked the original thread.