There once was a time where you had good radioshows. Hell, there even was a time MTV actually stood for Music TeleVision.
However, the rise of 'payola' meant a decline in musical diversity on the radio's and even on MTV.
At this point, the cassette trading with friends got really popular, people would give eachother cassettes to listen to(and copy).
Later on, came the internet radio's that catered to specific publics that allowed people to yet again discover new music from smaller artists.
Fast forward to today: A lot of internet radio's have been killed and the few remaining ones are eighter access restricted (pandora is US only) or only available through subscriptions (last.fm & consorts). I happen to be a last.fm user and I live in Europe. This service is only available to me for a monthly fee, won't run on mobile devices (apperantly, the labels have seperate licences for internet access on a PC and on a 'mobile device', go figure) and still restricts various artists music from playing in several regions.
I still buy CD's, mostly from smaller artists, but were it not for the internet and piracy, I'd have less then 1/10th of the amount of CD's & albums I have now.