Still, if Apple really wanted this to catch on, they should have made an Android and a Blackberry app/client for launch as well. It really should be cross-platform, and Apple has a history of screwing up the adoption of new standards they develop in exactly this manner.
Apple makes their money from selling hardware.
If they provide a software solution for other platforms, they do not provide incentive for people to get on their platform. (Not to mention, they buy themselves quite a few headaches making sure their software works with other platforms that they have NO control over.)
I would wonder who was running things in Cupertino if they DID provide apps/clients for Android and Blackberry.