The idea is to have all BlackBerry owners in the one place so they can answer each other's questions about certain applications and discuss all the ins and outs of owning a Blackberry.
There's very little to go on at the moment. Just a landing page with an introductory video that details pretty much exactly what we've said above. TechCrunch has managed to dig up some additional details, though. According to TC, the MyBlackberry community will be personalized, depending on what type of Blackberry you have. In other words, if you have a Pearl or a Bold, you don't have to listen to everyone complaining about the haptic touch on the Blackberry Storm. We assume this set up will involve selecting your device during registration.
RIM has said the site will also be there for prospective Blackberry owners so we assume you can sign up, select the model you're thinking of buying and browse through the relevant tips, tricks discussions as normal.