Over the years there have been many attempts to create a service to help users find similar minded BBM friends. I have always been holding out hope that RIM would provide such a service themselves but knowing RIM legal I doubt it. Until then the latest attempt to crop up is called SearchBBM which has both a website and BlackBerry smartphone app designed to help you find friends and share your PIN with them to chat.
I can kind of see the appeal especially considering how App World reviewers have taken over the review sections of App World to find BBM friends. Check out SearchBBM at www.searchbbm.com or download their app for free in App World.