I think you implied it with b) but availability of content is important as well. I've still got MP3s obtained via Napster and its ilk back in the day. The quality on many of them is below current standards, so I've been trying to upgrade to higher quality sources over the years. I'd say that I've got about a 20-25% success rate in being able to actually purchase that content legitimately. I could probably up that by 10-20% by going with overseas vendors, but I suspect most of those are bootlegged anyway.