Recently there have been a few stories of the iPhone OS 3.0 pushing our random messages that were possibly intended for someone else, but according to an article on appleinsider, the random message problem only affects those iPhoners who have hacked their iPhone and thus made it vulnerable.

The Apple iPhone generates unique public and private keys when activated which identify the iPhone to secure the pushed instant messages, and unlocking tools use duplicate tools to facilitate jailbroken use.

Thus with single identifying keys registered to multiple iPhones IMs are being pushed all over the show rather than to the intended recipient.