It's interesting to see Amazon & Google directly competing, to the point that Google rushes a seemingly incomplete cloud music offering (also without label consent) to counter Amazon's early control of the market.
They're also competing in cloud infrastructure, android app markets and streaming video services. Their fundamental services are not that different, both centered around search, though they don't really compete for it. Amazon is a retail service but part of their effectiveness is showing you what you want.
Supposedly the labels were asking Google to block torrent sites from search results. A store is the only missing feature and it just wasn't going to happen.
They're also competing in cloud infrastructure, android app markets and streaming video services. Their fundamental services are not that different, both centered around search, though they don't really compete for it. Amazon is a retail service but part of their effectiveness is showing you what you want.