There's an interesting feature on BBC Radio 4's Feedback programme this week, which addresses the multiple on-demand means by which young people explore music.
It includes an interview with a 17-year-old who describes how he switches between radio (to which he listens for 1-2 hours per day), online and other media (which consume another 10 hours a day), and what he looks for in a presenter. Then there's a response from the Head of Programmes for Radio 1, whose target audience is 15-24 year olds. He talks about "spread-betting" by making content available by traditional broadcast, podcast, interactive TV, and leaving the audience to choose which of these they prefer. He could have mentioned Radio 1's foray into Second Life, as well. In terms of presenters, he draws a distinction between "mood broadcasting" at specific times of the day, as distinct from "trusted guides" who are filters specifically for discovering new music.
The feature runs for ten minutes, and you can hear it for the next seven days via this link (RealPlayer plugin required). It starts 16 mins 45 seconds in.