Bittorrent does not work great, to my mind, compared to a centralized service. It's absolutely abysmal on network traffic, is inherently slow, and depending on the communication, practically unusable outside affinity groups. Toward that last end it's useful, but i'd hardly consider it great in general.

I don't know enough about Bitcoin to say if it's efficient but i'm aware that transactions can move around the network without much effort, which is nice. But there's big downsides to the transparency of transactions there vs cash or credit, not to mention having your "wallet" stolen vs more traditional credit systems that are more durable for general global commerce.

Both of those things are useful. They're just not as efficient or reliable as a centralized service can be. Centralized services & communication have their own problems, but generally speaking the bigger they are the more robust they are, which is often the opposite in truly distributed systems.