According to Strategy Analytics' just-published study from the fall, it's Apple's iCloud and iTunes Match that are top dogs in the US at a combined 27 percent of usage -- a not entirely surprising lead when Apple has pushed hard on iCloud's media syncing since iOS 5, and has large swaths of market share in MP3 players and tablets, not just smartphones.
For example, the usage of virtual currencies, online bartering marketplaces, and time banking brokers that match skills to needs and allow prices to be set mutually and in non-monetary units.