MonstaMunch: I think the OP has a valid point in the simple fact that GOG specifically states in it's privacy policy that "We do not share your personal details with outside third parties without your consent."
d2t: Order value per some random order number, without attributing it to any user ID/number/name, is not a "personal details" by any standards. This is an anonymized stat, so no, the OP doesn't have a valid point.
The problem is quite different here - is Google maliciously using this anonymous GOG.com data by linking it to certain Google Accounts.
That's not the issue by a long shot. The issue here is disclosure, which evidently hasn't been provided. You may not mind people storing and sharing your IP address at their discression, but others might. They have a right to make an informed decision.
And yes, I would like any details of financial transactions I make not to be passed on to third parties without my direct and explicit knowledge, even if you don't care.....
If someone gets your IP and your order numbers as well as info on what games you are ordering, they can find out what city you are located in, who your ISP is, and have a direct route in for gaming related phishing scams. Is that a legitimate concern? Maybe, maybe not, but you don't get to answer that for everyone.
d2t: But, you can also assume that Facebook and Twitter know of your every move whenever you visit a page that includes a Like/Follow link. Like the one you're currently on. If you don't like such possibility, my recommendation is that you DO NOT use accounts at companies you do not trust with your data and sit behind an anonymizing proxy.
And this is my point. You may think TwitFace is cool and fine, I don't, which is why I don't have an account with either, and never will. Again, that was my decision to make, not yours, and not anyone else's.