As shown in the grid below the apps that make it to the Core Utility quadrant are: Funwall, Superwall, and Topfriends. These are the monster apps on Facebook.
The apps I've highlighted in the Contagious Facility quadrant are: Movies, SuperPoke!, XMe, Likeness, and Causes. If we stripped out Funwall, Superwall, and Topfriends we'd probably get some presence in the Niche Utilities quadrant, but so far this quadrant is empty, but watch this space. The Low Impact quadrant is the most populated. I've only included the top 250 apps on this chart, but there are thousands of them that would cluster in that bottom left hand corner. The app market is a long tail as the chart below shows. This is a 'rich get richer' network effects model, where the most successful apps will grow because they are already successful.