Bitgrail is down so they have all that XRB locked up. Mercatox is semi-functional and confirmation emails for new accounts are not being sent out so a lot of people can't sell there either.
Yeah that's pretty much the reason. There are more than a few of us holding lots of XRB who could crush the price down but there isn't a good way to do that right now. I almost considered selling some on BitFlip the only other exchange trading it, but that looks like the most ghetto exchange I've seen so far. I wouldn't trust it with $1.