It's been a huge source of Hollywood profit but the silvery, lucrative DVD could be consigned to the pages of a history book if plunging US sales continue for the rest of the year. Sales of new titles tumbled by nearly one fifth in the first three months of this year, a decline fuelled partly by a lack of hits and the timing of Easter – but also by the start of what appears to be an irreversible change in consumer habits. The sale of DVDs has been falling since 2007, but the Digital Entertainment Group (DEG) reported that physical...