The Twitter-integrated challenge system in Blur allows players to send friends times to beat, regardless of what platform they use. Bizarre Creations says they'll also be sent as Xbox Live dashboard messages, allowing for some multiplayer without a Gold account.
The difference, of course, is the challenge doesn't take place head-to-head. Friends get a message (editable by the sender) containing the results and other information from the sender's race and a challenge to try to beat it. He's then free to do so on his time.
Bizarre Creations told MTV Multiplayer the challenge-message system was conceived because the studio's design staff had friends flung across the globe in vastly different time zones, or were leading busy lifestyles that didn't have them online at predictable times to race against friends.
"A lot of us have kids and family and stuff, but we're finding that as we're getting older we're just not able to get everyone together to play at the same time," lead designer Gareth Wilson said.