Music store iTunes has become the leader in the digital video market too.

Billboard reports that figures from an NPD Group study estimates that iTunes accounted for 67% of TV show sales in terms of units in 2012 (bringing it in-line with its music market share of 63%), 65% for feature films and 45% of on-demand video rentals with its nearest competitors trailling with market share of less than 20%.

Another NPD report, released in March, showed the relationship between ...