My current favorite for a crash and burn is WeWork and other shared office space providers. Their valuation is in the billions. They have signed long term leases for millions of square feet, and spent huge amounts of money purposing the space with high end amenities. There are at least a dozen companies engaged in this business model, with enormous exposure. Their clients sign short term leases, leaving all of the risk on the lessor when the economy slows down, which, at some point, will happen.