Starting March 2 2010 you can register to play the Blur Multiplayer Online Beta.

If you are interested you can sign up for the beta at their site.

Link to Official Site

Blur is the ultimate Powered-up racing experience, dropping you into electrified action with a mass of cars targeting the finish line and battling each other as they trade paint. Travel the globe from L.A. and San Francisco to Spain, the UK and more to take on the best the streets have to offer. Utilize an arsenal of Power-ups like nitro speed boosts, shock attacks, defensive shields, and landmines to beat your rivals across the finish line. You choose how and when to use your armory of Power-ups for ultimate impact in a race where the outcome is never certain. Blur’s story unfolds through a unique community-based social network interface that includes 4 player split-screen multiplayer and online multiplayer up to 20 racers.