Disclosure: I work at SimpleGeo. You're right, copyright does not protect facts _in the United States_. Rules differ around the world. In the EU, for instance,

Disclosure: I work at SimpleGeo. You're right, copyright does not protect facts _in the United States_. Rules differ around the world. In the EU, for instance, there's a "sweat of the brow" criteria for database protection. Even in the US, though, copyright law is largely irrelevant. When you sign up to use a web service you generally accept terms and conditions that lay out exactly how you're allowed to use the service and the data you consume. From that point on your interactions with the service are regulated by those terms under contract, tort, and other common law statutes. If the terms say you're not allowed to redistribute the data then doing so would be violation of contract and you would be liable for damages. Basically, things get really messy really fast. I'm an engineer, not a lawyer. So, honestly, I'm not an expert on this stuff. But I think most engineers agree that the current situation is sort of stupid. Philosophically I agree with the copyright law as it stands. Facts should be free. So CC0ing the data is just an explicit, formal, contractual statement that we're not limiting how our data can be used anywhere in the world.