When Napster was about I revelled in it. It was astonishing, the depth of the catalogue was unlike anything we've seen before.
After that I didn't really get into any of the other sharing networks, too hard, too seedy.
Now YouTube more or less fills that gap. Great place to find odd songs and nostalgia. Stuff you couldn't buy if you wanted to. And it is linkable so sharing is as easy as posting to Tumblr.
I spent a few years buying the occasional album from iTunes or Amazon. Now I use them for TV shows and the occasional film. I'd use iTunes more if their catalogue was deeper.
Spotify has changed the game for me this year. £5 a month for unlimited ad free music. Not quite the same depth of catalogue but good enough for day to day listening. Having the reviews and biographical details of the bands available inside, the interface as well as influencers and related artists, is what has really altered the way I approach music. I not only listen but I learn about the bands' context, their critical reception and who else I might enjoy. And I can just wander this web of linked music at will not having to worry about how much it will cost me.
Russell, FWIW I don't really need a bauble or a trinket to be convinced to contribute. The content is sufficient. I'd be happy if there was a yearly reminder to contribute something.
After listening to a bunch of NPR pledge drives while in the US I came conclusion that the logo emblazoned "incentives" they gave to their contributors somehow distracted from or devalued their excellent content.