A survey by YouGov shows that online tv viewing in the UK has risen by 54% since 2009, with 55% of 18-24 year olds watching internet tv at least once per week more than the 36% of 18-24s and 30% of 25-34s.
News seems to be a major driver. The availability of live news channels on the web meant that 56% of 18-24s go to the web as soon as news breaks, more than the 13% who go to newspapers' websites.
This would also seem to indicate that there's mileage in serving news channels on mobile devices.