She would have to be like what, 14 at the time the video was supposedly made?
I think the REAL issue here is why the original uploader had a video like that. I think he needs a visit from the Korean version of Chris Hansen.
Other than that, I don't care whether or not it's her. She's still Jiyeon. If it is her, we've loved her even despite it for a long time already, I don't see why knowing it would make anything different. If it's not her, everything is the exact same.
Either way, anti-fans are retarded.
The best thing to do for Jiyeon right now would be to give her lots of support. I already left her a nice message on Twitter; I advise everyone else do the same or something comparable.