Im a longtime Blackberry user, and love it, mainly just for how simple, functional and good it is at what it does...but recently i also realised just how important it is at keeping me connected with my friends, not just work related stuff.
A really close friend of mine recently left bb for an iphone, and its shocked me how little we talk now day to day. yes, sending a txt message is physically exactly the same as sending a bbm (an arguement i've had alot over the past couple of weeks!) but actually, for some reason its not. I talk reguarly with my bbm contacts, even to people im not that close to. status updates, pictures, what people are listening to etc...it really does 'connect' you with other people. We now joke that our friendship was obviously purely based on us both having bb's as we now seem to be drifting apart!
For all of blackberry strengths this i think is a big one, and i know loads of people who would never leave bb purely because of bbm...its unfortunatly also something that non bb users wont understand until they are part of the circle. whatsapp is no bbm, theres no comparison...i wouldnt give a stranger my phone number, but id gladly give them my pin. I'm not sure about elsewhere, but in the UK the blackberry is never really marketed in that way, its a 'work' phone. Through word of mouth though alot of 'non work' people are getting blackberrys are becoming part of their own bb 'social network'...going forward I really think its a strength RIM should be shouting about, and not mentioned as an after thought...
Just the rantings of a happy blackberry user...:)