Why would I need BlackBerry Messenger on Android and iPhone?

It would be cool to have BlackBerry Messenger (BBM) on an iPhone or Android phone, since I'm very familiar with BBM interface. The challenge today is switching from BBM, Google Talk, Yahoo IM, Whatsapp to keep in-touch with my friend and family, and business colleague.

For BBM to be effective on the iPhone and Android, it MUST BE fully integrated with the current BBM server, which is proprietary to RIM. If  the integration is lacking or missing, then it is just another app on the iPhone/Android phone, such as Whatsapp.

What is the benefit for Apple, Google, or RIM? RIM's BBM is one of the app on BlackBerry that is a huge customer stickiness. If RIM looses this stickiness they will also loose some customers.

The major benefit would be to Apple, Google, and RIM customers. The losers would be  MSN, Google Talk, Yahoo IM, etc...