h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

These spawn of the devil have been invented for lazy people who don't like making beds. All duvets should be piled up and burnt (synthetic versions will obviously have to be incinerated under controlled conditons to avoid pollution). Once that has happened, we can all sleep soundly in our beds again with no danger of the dreaded "feet-sticking-out syndrome", the fastest route to wakefulness since the invention of the alarm clock.

Easy to handle as they are, duvets cause problems during summer. With a sheet-and-blanket bed it's possible to throw off layers when getting too warm and gather them up again when your temperature has stabilised a little. Duvets don't give you this option, Melt or freeze, there is no mid-point.