One way to deal a death blow to a fad is to declare it unsafe. This is what happened last week to hoverboards, the star transporter of last Christmas season. The Consumer Product Safety Commission declared them all dangerous, no matter the brand or price point. None will be allowed to be sold until they get an Underwriter’s Laboratory certification. One wonders how the product reached these shores without it. Once a manufacturer does receive the UL mark, it can start again to build and sell the machines, but the unknown is whether anyone will buy them. They are not easy to use and there are numerous videos of people falling off of them. They could easily go the way of the Pet Rock — a brief popularity followed by nothing. If so, it would not be the first or last fad this happened to. Like the Segway, which was supposed to be the mass transportation vehicle of the future, the hoverboard may recede in public consciousness.