The gentle rise of the machines

WHO would have thought that a Frisbee-shaped contraption that extracts dust from carpets would be the state of the art in household robots at the dawn of the 21st century? In the past year, Roomba, a circular automatic vacuum cleaner made by a firm called iRobot, has swept up millions of dollars from over 200,000 buyers--and was a must-have at Christmas, among geeks at least. Rival firms such as Electrolux and Karcher sell similar but pricier sweepers. Robot vacuum cleaners, it seems, are catching on. Are these mere playthings, or the beginning of a new trend?