The scale of Facebook and the role it plays in today's society stems way beyond the newspaper. In an age where communication mainly happens online, it is more comparable to a telephone, or even the internet itself. For (hundreds of) millions of people, Facebook IS the internet. You could say "well $telecom can choose to censor certain words that go through their phone lines, or block websites, just like a store can choose to stock a particular product or not" but let's be honest, they're different scenarios.