Been thinking about leaving BlackBerry but can't drop BlackBerry Messenger? RIM is hoping they have an add-on for the service to keep you hooked in: BBM Music. The $4.99-a-month service will give you access to stream (and locally store) a maximum of 50 songs, initially. In order to enforce that 50-song limitation, RIM will prevent users from changing more than 25 of their chosen songs per month. Crazy, no? Actually, it might be crazy like a fox: users can grow their libraries of available music by connecting with other BBM Music users. Once you build your BBM Music social network, you'll have access to your friends' 50 songs as well as your own.

The idea appears to be this: as a part of an overall BBM-enabled app push, RIM can make BBM even more addictive and viral by attaching real rewards to converting other users. It could be genius, if it weren't so ridiculous in the face of other all-you-can-eat streaming music services like Spotify and RDIO, which both offer some form of social music networking.

If you're still interested, you can sign up here to be notified when it's available for you. As of right now, the service is currently launched on a limited trial basis in the US, Canada, and the UK.

Source: RIM Blog, RIM PR; via CrackBerry