MP3tunes boss Michael Robertson has tossed another rock into the bubbling pool around Amazon’s new cloud music service, writing a column for TechCrunch outlining what he claims are the major labels’ demands when licensing cloud music services. According to Robertson, UMG wants only songs with embedded ‘digital receipts’ to be able to be uploaded into lockers, which would nix songs ripped from CDs as well as piracy. He suggests Sony Music Entertainment is more worried about users sharing lockers with friends, and also wants to only allow people to download files from their lockers once each. Meanwhile, Robertson says WMG is worried about people having multiple lockers then sharing them with friends, and did want a ‘central locker authority’ to prevent this, although he suggests this has since been relaxed to a demand that locker identities be tied to specific credit cards or other ID. “The above list of demands is by no means complete but rather an illustration of the labels mindset. There are others issues dealing with simultaneous user access, family accounts, mobile access, local caching, regional restrictions and more,” writes Robertson.