A new form of consumer activism is sweeping across Europe. Young people join up to buy all the goods in shops whose owners are willing to introduce environmentally friendly technology.This is how it works: a group of 200 youngsters arrange to meet via SMS and Twitter, rush into a store and buy up all the merchandise if the owners have pledged to make their business more energy-efficient. The so-called Carrotmobs originated in the US and the notion is finding plenty of imitators in Europe. This form of activism seems tailor-made for young people who want to fight global warming and party, too.