Revenues are soaring for makers of apps that run on the 400 million-member social network. Here are players to watch

Zynga

Est. 2010 revenue: $450 million*Game registrations: 253 millionBiggest hit: FarmVille

RockYou

Est. 2010 revenue: $80-$100 million**Game registrations: 71 millionBiggest hit: Zoo World

Electronic Arts

Est. 2010 revenue: $100 million***Game registrations: 58 millionBiggest hit: Pet Society

CrowdStar

Est. 2010 revenue: $100 million**Game registrations: 47 millionBiggest hit: Happy Aquarium

Playdom

Est. 2010 revenue: $100 million**Game registrations: 39 millionBiggest hit: Social City

Slide

Est. 2010 revenue: $30-$50 million*Game registrations: 21 millionBiggest hit: FunSpace

Digital Chocolate

Est. 2010 revenue: $30-$40 million*Game registrations: 2.1 millionBiggest hit: MMA Pro Fighter

* Bloomberg Businessweek reporting** Company data*** Wedbush Morgan Securities

Sources: Registration data from AppData