You shouldn't have to lock your data down. I can see GPL'd code and can use it and distribute it but I can't close source it and then resell it as a proprietary app and then say "hey if you didn't want me to use it you shouldn'thave made it available". That is the license we agree to. A clear license lines out acceptable use and it looks to me like they are trying to strike a balance between being solvent and user friendly. But freeloaders will ruin it for others.
I agree you shouldn't have to go to any extremes to lock down your own data. But when publishing an website online, there are certain standards you need to follow if you don't want people copying the data on your website. If they are allowing search engines to index their proprietary data, then they should have no expectation that others will not do the same.