I haven't personally owned a BlackBerry smartphone for long enough to get into the whole BBM craze, but understand it is quite addictive and I did enjoy it when I was using an eval BB for the last few months and if RIM ever releases the Bold 9900 I may get one for myself. Tonight RIM announced BBM version 6 with greatly expanded social functionality that lets application developers integrate a BBM experience into their apps and services.
As you can see in videos on the BlackBerry Blog you can chat with friends on BBM within games, use Foursquare to check in and then notify a friend via BBM that you are there, and even share apps with friends via BBM 6. This new version will run on BlackBerry smartphones running BB OS 5.0 and later and is not available through Bridge on the PlayBook.
It looks like a nice step forward for BBM as a platform and I think it will be quite handy for the sports apps listed since you can interact with friends as you are following games live and may help make games a much more interactive experience without requiring you to use some kind of in-game chat client or experience.
It may take up to 24 hours to get BBM 6 on your device in BlackBerry App World so be patient if you are looking for this new client.