I'm not a fan of Coinbase either just because of the fact that they ask you for real information's before being able to use their services (buying / selling coins).
However, their API seems to be working just fine :
https://coinbase.statuspage.io/I'm with the security measures though since it protects the users , that way customers accounts don't get hacked that easy. CloudFlare in the other hand is added for security measures as well and using HTTPS is better then HTTP If they don't want the bank accounts information's and credit cards compromised . I don't understand what do you mean by "block transaction or spy on transactions since everything is available on the blockchain. Other than that , I don't even see why would CloudFlare do that to in the first place.