Facebook operates on a scale that is many orders of magnitude larger than BB. You could argue that Facebook is approaching a de-facto monopoly of sorts on public social networking “expression”.
No such argument is remotely possible for BB. Until your service is world scale, and can be plausibly viewed as a public utility in practice, it has no obligation to represent “everyone” or otherwise present itself as a fair and equitable place where all speech has to be allowed, provided said speech does not literally violate the law.
Facebook’s tagline
Connect with friends and the world around you on Facebook.
BB’s tagline
A directory of (mostly) wonderful things
BB has always presented itself as a place for Happy Mutants. Not a place for every living human being, like Facebook.
