Just because overstock is using coinbase doesn't make it any less decentralized. Either party on both ends of the transaction can be using coinbase, or they can

Just because overstock is using coinbase doesn't make it any less decentralized. Either party on both ends of the transaction can be using coinbase, or they can use another service, or they can just send things manually via the commandline (bitcoind, et al). If they were using something like dwolla, then as a consumer, I too would have to use dwolla ... but bitcoin is open.