In-flight Media: Taking the Captive Audience for Granted?

The argument in favour of targeting air passengers has always been that they are a captive and highly desirable audience with little to do but read or watch what's put in front of them. But now that budget airlines are providing much of the growth in passenger numbers, and there are so many ways to hit travellers with advertising in the air, is the impact of in-flight being jeopardised?