At first I believed my thoughts revolved around iTunes Match but really they just revolve around Cloud-based streamed music content. Streamed music takes bandwidth and data allowance. Since when you’re out and about on 3G (not WiFi) bandwidth is so variable and since data allowance costs a lot of money (I get 1.5Gb per month but it costs $59/month to get it). Assuming I personally had all of music stored in the cloud then I could continuously stream music for 34 days - by which time I would have a new quota. It’s feasible but then most people don’t have a 1.5Gb quota (usually 200Mb and that lasts about 4.5 days continuously).
Yes, I know that people won’t listen to their music streaming continuously however the arguments are these: why not buy a 64Gb iPod Touch or iPhone and fill it with your music rather than stream it? Certainly the model costs more than the others but the cost of a bigger data plan to accommodate this would cancel out in less than a year for most people. Add to that the variability of 3G coverage and the certainty of being able to listen to music locally stored and there’s no argument.
I do see a place for a-la-carte music streaming services - but that is more of an impulse desire to listen to any song in existence whenever you like. iTunes Match isn’t that - nor is Google Music [Beta] nor is Amazon Cloud Drive. The appeal of these services will be niche at best until the cost of data goes down and the bandwidth and coverage of 3G and 4G networks improves. Even then, with the cost of flash storage falling all the time, it will still be a questionable proposition for most.