When Facebook Chief Executive Mark Zuckerberg recently announced a "Like" button that publishers could place on their Web pages, he predicted it would make the Web smarter and "more social." What ...

When was the last time you clicked the Like button on some piece of content outside of Facebook, causing anyone who sees your Facebook activity to see your little recommendation in their news feed?

It was summer 2007. Facebook was three years old and growing at a heady pace. Originally for college students, it had opened to the public the previous fall. Now it had 30 million users. What it ...