Although, there is material that *is* appropriate for adults but not children. I can't come up with great examples, but say, commentary on certain parts of the Old Testament or NFP stuff? Any thoughts on these?

For my two cents, this still doesn't call for gov't censorship, but maybe some kind of browser-based parental controls? A site could send a header or something with the recommended age, that the owner of the device could opt into? Then mom or dad says the user of this device/account was born on this date. Don't allow these kinds of content without parental approval.