I see the pro's- make new friends and go to their weddings (free food + fun), possibly win a free trip, get the footage without hiring a videographer, get to wear your dress again when they do the little "everyone stand around laughing and pretending to have fun in your gown" segment
I see the con's- having to listen to negative things about your wedding "my steak was dry, she didn't have enough real flowers", being kind of awkward at the other weddings since you don't know anyone, having a camera crew may make the wedding less intimate.
I don't know if FI would ever go for it but I think it would be kinda fun- what do you think?