2. The new timeline reinforces consistency across Facebook. To the extent that Facebook can make pages (for brands) the same as profiles (for people), this makes the social network more user-friendly for advertisers.
3. The new timeline, especially the prominent cover image, reinforces the importance of visuals on the web.
4. The new timeline decreases the prominence of tabs, which many users have put considerable time into creating and optimizing.
Addendum (2/29/2012): Success!