Amazon's AWS held steady at 33 percent of the worldwide market share of cloud infrastructure service providers in the first quarter, according to Synergy. And though it grew just 43 percent in the first quarter, Amazon's cloud revenue is more than the next five providers combines, Synergy estimates.
To be sure, that doesn't mean there isn't money to be made for other major players in the cloud. Credit Suisse expects Microsoft's cloud to continue growing at a pace of more than 50 percent revenue growth until 2018, boosting profit margins with its key advantages, including regulatory compliance and international penetration.
Google also talked a big game on a conference call with investors on Thursday night, highlighting that headcount at the company rose thanks to investment in cloud centers and engineers.
But Trip Miller, the founder of Gullane Capital Partners and an investor in Amazon, told CNBC that space is still essentially an oligopoly.
"No one else of any meaningful size outside a handful of major players is getting into it because they can't afford to get into it," Miller said.
— With reporting by CNBC's Ari Levy
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