The very notion of a service like coinbase is problematic, and coinbase's implementation is especially poor for privacy. First, they are taking an inherently t

The very notion of a service like coinbase is problematic, and coinbase's implementation is especially poor for privacy. First, they are taking an inherently trustless system and demanding a very high level of trust for AML/KYC requirements, which is unavoidable when dealing with fiat conversions. Why not just trade directly in bitcoin (of course few people want to do this which is why coinbase exists)? Specifically however, coinbase by default keeps your private keys under their control, which is where the bigger violation is IMO. They push everyone to go through their service and not use bitcoin directly, so they can track and control everything. The blockchain may or may not even be involved in some of their schemes (they offer a fiat-fiat service that supposedly involves bitcoin!). This is inevitable, as they are a company out for profit not an idealistic bunch of ancap hackers, but they are not just looking at public blockchain data. Even their name is a conflation, coinbase is a technical term for the block reward transaction.