I'm against the idea of a symposium because, and I know this sounds harsh, I'm concerned about people "educating" others that don't know what they're talking about. I'm not saying it's particular to this forum. It's every forum. Every website. The other day I read a professional article that said a $10 bullet was the best sex toy ever. Period. I think many of us would disagree, or at least say YMMV. The point is that I would think the "educators" would have to talk to a mod in advance about what they are going to be talking about and demonstrate their knowlege, not just talk.
But, I should add, if they are going to do that, that would be a workshop. It is the way the workshops are currently set up, in fact, or at least they were. And as far as it being a live discussion or posted lesson, they are one in the same in a forum. You can always go back and read it later, whether you were there at the time or not. You could even have a sticky post at the beginning of the lesson, posted after the workshop is done, for people who just want the cliffnotes version.
Further, I am against giving points for people just attending. It would just be another way to abuse the point system and not garner any realiable feedback on the project. Plus, there will always be people complaining that the times don't work for them. Everyone is a little happier to be paid to do something, but that doesn't mean they are contributing.
As a final note, I'd like to add that most of the suggestions made so far are actually the way that workshops are currently set up. Really.