A few years ago Google came under fire for sending extra identifiers to Google's websites in a header named X-Client-Data[0]. I don't remember how many identifying bits that includes or whether they still do it, but it was the tipping point for me.
- Extensive evidence provided by brave national heroes and civil rights legends like Edward Snowden and Chelsea Manning, including training materials for specific named NSA programs like PRISM that offer explicit lists of cooperating partners, including Google, Microsoft, Apple - basically every big tech company, but also smaller but popular ones, such as Skype (pre-Microsoft acquisition); this is well known among technology's civil rights advocates, and isn't hard to find discussion of by credible technologists, including the folks behind Protonmail¹
- Elon & DOGE: see literally every major American news network besides Fox pretty much since the inauguration, large swathes of the internet, several prominent discussions on HN. It's not just illegally mass-surveilled stuff either, they're going through all sorts of classified stuff right now!
Source?