To look at my email inbox is to see that last week's coverage of cloud computing caught your attention. Not all of you were complimentary. Some wondered where my head was when I called EMC (NYSE:EMC) a disk maker when, in fact, it does much more than that, including its own set of cloud computing services.

More of you, though, like (NASDAQ:AMZN) as a cloud computing company. You argue that its S3 and EC2 offerings -- otherwise known as rentable storage and computing power -- are game-changing, and that Amazon is way ahead of everyone else in this area.

I'm not so sure. Amazon has limits on what it can offer because its infrastructure is first responsible for managing a massive e-commerce business. IBM (NYSE:IBM), which last week announced a $400 million commitment to expand its cloud computing infrastructure, has no such conflict. Unlike Akamai Technologies (NASDAQ:AKAM) and (NYSE:CRM), it's the cloud computing giant you don't know.

IBM operates a vast network of global data centers and, last November, unveiled what it calls the "Blue Cloud," which in many ways apes what Amazon offers but also goes further. Big Blue's clusters are based on its servers and software and come with access to the company's vaunted professional services organization.

We don't yet know how IBM is pricing "Blue Cloud" or what it'll mean for its bottom line. But think about the company's business model: If its professional services unit continues to lead others, IBM should do whatever it must to get really good at creating cloudy clusters. That means investing in infrastructure; $400 million for new and revamped facilities in Tokyo and at Research Triangle Park likely are just the beginning.

More clouds are forming in Big Blue's skies. Don't be surprised if they rain billions.

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