Of the 145 galleries in the Victoria and Albert Museum, the modern ones are the poor relations. Tucked away behind the National Art Library in a remote corner of the third floor, they provide a rather perfunctory coda to 3,000 years of decorative arts history. But now the coda has a sting in its tail.This summer, the museum opened its new Rapid Response Collecting Room devoted to changing displays of contemporary objects selected for their sociopolitical, rather than their aesthetic, interest. What distinguishes the dozen objects in Room 74a from the 4.5 million others in the museum’s collections is their relative cheapness: the £6 pack of Cool Kitty Katy Perry Lashes could have been acquired with the petty cash, and probably was. Another difference is that, unlike the divisio