Other differences: Facebook had MySpace and other early social networks to see what they did wrong. In addition to just the general not-keeping-up-with-the-times, the excessive customization + bored teens = eyes bleeding & having to look at different places on a page to get the same info. Although it's gotten worse it's still cleaner than MySpace was during its heyday. Also, Facebook has Zuckerburg. Whatever you say about him, he's smart and focused on keeping users, so there's constant tweaks to see what will keep them.