Just imagine that few websites you buy from use coinbase and you don't care much and buy from the same address, well what will this mean for coinbase? Who knows if coinbase and other payment proccessors aren't working together and are conecting the dots of who is moving and buying what. Imagine what impact on privacy this would have.
This is definitely a thing to consider, I'm not sure what is coinbase policy with account registration, do people are required to give them real personal informations? If yes, than anonymity is already lost. Never was a fan of this "wallet", to much strange informations where floating around, regarding withdraw issues, frozen accounts and in general rather worrying stuff. If someone asks me, I will always dissuade usage of this platform. When I stumble upon a shop that sells stuff through them than I'm probably not going to use it.
First part of your post is also very adequate, I don't like how merchants instantly swap coins to fiat, it feel so opportunistic (but hey, that's just business), doesn't do much good in bigger picture perspective.
The only upside I see here is BitPay now has a competitor...
Fair point, the more the merrier.