For your consideration, an article from The Economist. Perhaps more of an intro-to-cloud than some around here need, but it includes the story of how a couple of folks were able to determine the size of (at least part) of Amazon's cloud. It's a cool story that involves German tank manufacturing practices from World War II ... take a look! At one point last year "Amazon’s annual cloud-computing revenues (were estimated)at between $500m and $700m in 2010" but seems those numbers might be low.

Tanks in the cloud - Computing services are both bigger and smaller than assumed
Dec 29th 2010
www.economist.com/node/17797794

Thanks for this - the article you link to is interesting. FWIW, I'd question anyone's ability to forecast base-level cloud services out to 2020 - Forrester isn't a great starting point (their strength is more as commentators than forecasters), the environment is likely to change quickly and unpredictably, and there's no allowance anywhere in here for "private cloud" - which might complicate the discussion, but is no less real for that.

To that last point - in a recent editorial conversation, the IT in Canada staff was debating where "cloud" ends. It reminded at least one of us (okay, me!) of client/server, where ultimately, everything connected to a user or a server was subsumed into the definition. Will this happen with cloud? Hard to say, for us, Forrester, or The Economist - but I think we can say that as we see more IT firms recognize value in aligning their offerings against the cloud market, we'll see more offerings falling broadly under an every-expanding - and ever-more-valuable - cloud umbrella.