Hey thanks! As the market value goes below a certain point less Steem dollars are created. Currently there is only $3million in Steem dollars out of $465million in value so that's less than 1% so it would have to go down 99%! Also even if that were to go down that much you get a certain amount of Steem collateral that may be temporarily worth less, but you'll still have something. Just like if you backed money with real estate the real estate value may go down and you may end up getting the real estate collateral instead of money. Eventually the real estate may be worth more.