When you log out of Facebook you may see an ad that looks like a Page timeline on the homepage. This allows advertisers to show larger format ads on Facebook without interrupting your experience when you’re logged in and connecting with your friends. Advertising keeps Facebook free for everyone.
I certainly don’t have any data on this, but I imagine that very few people actually log out of Facebook instead of just closing or quitting their browser window. And if they do, it’s probably about once a day.
Does this seem like a good use of advertising dollars? I also like the closing line as it implies that users better like the big ad or pay for Facebook.