Let's say that, after ownership of facts is established, a database company thinks you are using some of its content. They file a lawsuit, noting that a lot of the information in your database mirrors theirs. They do have the burden of proof, but during pretrial discovery they're going to ask you where you obtained that factual information. If you can't explain how you got it, save for from their content, you will be in trouble.

Let's say that it is The Political Graveyard versus EvilDataCorp, a multi-billion dollar publishing house. Let's say that The Political Graveyard is sued, defends, establishes that it obtained the data from legitimate sources, and the suit is dismissed. How much do you suppose that small, educational, public-interest project would have paid in legal fees and costs by the time of the dismissal? Somewhere in the five figures - maybe more? (As a lawyer, Larry might be able to do it for less, but you get the point.)

Now let's assume that EvilDataCorp, the multi-billion dollar publishing house, develops a database of information that is, at the time of its inception, unique. Rather than allowing competitors to emerge, EvilDataCorp sues any company which creates a competing product claiming copyright infringement. Assuming it can successfully tie up its legitimate competitors through the litigation process, it will achieve two ends: First, it will remain the sole source of information; Second, it will deter competitors from trying to enter the field as they know they will be sued. If it is sufficiently aggressive, competitors will assume that it will follow the same model with its future products, and again competition will be deterred.