Evil Avatar has their review up for Burnout Paradise on the Xbox 360 and Playstation 3.  The game features and 8-player co-op mode available online. 

Online freeburn with 8 people is a blast with over 300 challenges for online play, not to mention the ability to create your own races with or without checkpoints.

Those few complaints aside the online mode is a friggin blast to play. With a ton of unique and fun challenges to complete with friends, it'll keep you entertained for hours. The other great thing is the mug shot aspect of the game. If you have the Vision Cam on 360 or Eye Toy on PS3 you'll be able to send a picture to an opponent online when they take you down. It's a fun little way to increase the banter that goes on.

Once you get online with a bunch of friends Paradise becomes a totally different experience that you lose hours of time to. I personally can’t remember another game that was so much fun to play online. Some of the guys from Evil Avatar and I were doing barrel rolls at the beach and we just kept doing them. Sometimes someone would accidentally hit someone else just as they were ready to attempt the roll, but everyone laughed it off and just enjoyed the experience.

Sounds like this is one you won't want to miss online.  I know from personal experience that the online challenges definitley require teamwork to accomplish, and some are very unique and inventive.  My personal favorite challenge?  Jumping from opposite ends of a bridge and colliding in mid air!