Facebook posts for Summative Assessment tasks?

As a result of the sad events in Paris over the weekend, Facebook is on fire with people from all over the world responding in various ways. Many have begun posting images of themselves enjoying Paris in happier times. Many have decided to paint their profile picture the colors of the French flag. And many are writing. Writing their thoughts and responding to the thoughts of others. There is considerable emotion involved in this writing, and it is clear that some write with emotion much better than others.

Some posts get the emotion through very clearly with some very strong language, but struggle to hold their argument together under the weight of that emotion. One ends up with the sense that the writer is upset/angry/etc but is not really sure what about.

Occasionally there is a writer who gets the combination right. Strong language, strong ideas, well put together. When I read those posts, I find myself considering an opinion that might be different to my own, considering a change to my own opinion on the matter. These are the posts that I click "Like" for. I like being brought to that point where someone has forced me to consider a new perspective through the clarity of their emotion and ideas in their writing.

So how are we engaging our students today to this level? What would they choose to write passionately about? What is it that would cause a collision of strong language and strong ideas, and how would we teach them to get the balance right?

I wonder if there are any teachers out there who have used a Facebook post as a summative assessment piece? If we are serious about asking our students to compose real writing for a real audience, then we SHOULD be using Facebook!