My online classes have occasionally included a few points for "participation". Some profs simply stated "thou shalt post thrice weekly to thy Blackboard forum", and that gets them off the hook for having to think about how to get online students to participate. They can show a metric to the department chair and say "see, 80% of my students are participating. Therefore your decision to mandate classroom participation online was a good and wise decision, o chair of my department." </brownNose>
The better profs didn't define participation. They simply said "I'll notice when you participate." The ambiguity encouraged people to speak up, ask questions, send emails, etc. I don't remember any case where the Blackboard forum was effectively used for "participation" in those classes.
Pretty much the only thing I ever remember people posting to Blackboard were whiny complaints about 'hey, I answered question #17 with A, and you said A and B, so I should get half credit right? And you should round all those half points up, so I will get a B- instead of a C+."