Electronic Arts is diving into the social gaming pool with its US$300 million acquisition of London-based social game creator Playfish.

Playfish will operate within EA Interactive, the company’s division focused on the web and wireless. EA put down US$275 million in cash plus US$25 million in equity retention arrangements. Additionally, the deal could be worth another US$100 million to the sellers if Playfish achieves a set of performance milestones, set by EA, through December 2011.

Playfish, one of the world’s largest social gaming companies, boasts more than 150 million games installed and played worldwide on platforms such as Facebook, MySpace, Google, Bebo, iPhone and Android. It has more than 60 million monthly active players across its 10 titles – including Pet Society, Restaurant City and Country Story on Facebook, which sees more than one billion game play sessions every month.