Every merchant can opt to be a bag-holder. But the losses should be minimal in all cases where the merchants sell goods with small marginal costs for them. The prime example for this are digital goods like music, movies and software.

Let's have a case where music and movie producers sell music and movies and with these assets "back" Bitcoin by guaranteeing the price for 24 hours. Now, a 20% crash happens. An "average Joe" (we must assume that he regularly buys movies and music) that has invested in Bitcoin, has the choice to accept the 20% loss or buy some music and movies for it that he wanted to buy.

If he cuts his losses and sells the coins with 20% loss at an exchange, he would drive the price further down - it's an invididual loss for him and also a loss for the Bitcoin ecosystem (at least, everybody that is owning Bitcoin).

But if he accepts to buy the media, he has made no loss monetarily (because he, as a music&movies lover, is satisfying an individual necessity), and the merchant has sold one copy more that costs him closely to nothing. So it would be extremely probable that merchants would achieve more sales in crash periods. It's a win-win situation for both actors.