- Your privacy takes a massive hit. Remember all bitcoin transactions are public information. If you reuse the same address over and over again everyone can tell how much money you are receiving and spending.
This aspect does not concern me as much as it should, but I understand the point.
So IMO making a physical QR code is a bad idea if it encourages you to reuse addresses. And don't even think about using an address that belongs to coinbase. There are so many things that could go wrong with that. What are you going to do if coinbase shuts down? Or gets hacked? What if you need to prove ownership of the address by signing a message?
Agreed, this is a risk. However, I would not plan on keeping much BTC in Coinbase's system -- I would only use it for transactional activity. The rest I would put in cold storage in paper wallets. Coinbase does allow proof of ownership by signing a message. (I have never done it, but I do see that option in the "addresses" screen.)
Thanks