1) Free publicity. When you download an app if you just ok it to death and don't pay attention to what your clicking all your bbm friends will see your status change to what you downloaded with a link for them to download
2) The most important. Bbm is a very secure way to communicate. Allowing it access to apps allows you to share things seamlessly with your bbm contacts. Like screem munches, game scores and some games you can actually play with your bbm friends also live.
Those are my 2 ideas. They may be wrong but they seem logical to me. Lol
Thank you all , if its only about sharing games and scores , doesn't matter , I thought its important.
As of right now no. With rim stating their intentions to make bbm a totally social platform I feel its a baby step into the future of blackberry integration.