BlackBoard should "opt out"
One of the comments makes a link here where the phrase "creepy tree house effect" is discussed, which is pretty accurate for a neologism.
One of the comments to the creepy tree house effect discusses, quite well, how she tried twitter as an opt in class aid.
To all of this I say: keep the class out of socializing. That is, by drawing a clear demarcation between class time and social time, a whole set of confusing, embarrassing, and/or inappropriate blurring of personal/professional.
Why would BlackBoard want to interface on FaceBook? Because students don't want to log on to BB's interface? Then create an RSS feed for updates to be spammed out.
Because students spend a lot of time on Facebook and not on the BB site? Then make the BB site more usable--key interfaces with the library, with sources, may a link-in with OneNote or the like...
Point is, quit trying to be "cool" and be functional. Let the students and profs work out the time spent on task, and leave the socializing to the hallways.