Gather IT executives in a room and talk of cloud computing billows forth. For CIOs who are already dabbling, projected savings are debated. From bullish analysts and eager vendors, more dazzling benefits are predicted.

Yet just as quickly come the caveats. Questions abound on security, reliability and control over corporate data. The biggest shadow of all is cast over what, exactly, cloud computing means.

A recent academic study identified at least 22 definitions of "cloud computing" in common use, from the broad notion of using the Internet to access any sort of managed technology services (also known as SaaS or software-as-a-service) to the wide-eyed optimist's view that a diverse, powerful lineup of cloud services will be delivered in real time by crash-proof distributed servers "without complicated deployment worries".

The sorry economy is prompting more CIOs to explore cloud computing and its cost-cutting promise, says Doug Tracy, former global CTO for Rolls-Royce. "But it's still an idea that a lot of people don't know a whole lot about."

The core attraction of the cloud is that companies can avoid buying and running hardware, software and other equipment by contracting with a services vendor to run selected systems or applications on its own infrastructure of virtualised servers. The "services" you purchase are delivered in a standardised, multitenancy fashion that observers say will save one-third to one-half of your current costs.

That's certainly appealing as this down economy forces CIOs to seek ever-greater efficiencies from IT infrastructures already as lean as starving wolves.

"We're under tremendous pressure to provide flexibility and agility and to be driving cost models down," says Charles Soto, vice president of IT at Motorola's Broadband Mobility Solutions business, which recently tested cloud computing services for four different applications. But thinking that cloud computing will release an instant reservoir of savings is a mistake, he adds.

To Arthur Winn, head of pricing at BT Group, "cloud" is nothing but a marketing term. The giant London telecommunications company has been doing what could be considered cloud computing for several years, he says. That is, handing over BT customer calling data to a third party to analyse and then let BT access via the Internet. "As long as we are getting more service for less money each year, we're happy," he says.

Making decisions about an over-hyped, under-delivering technology amid today's unrelenting economic pressures certainly isn't easy. So to help uncloud your thinking, we looked into exactly how several companies across various industries are experimenting with cloud computing.

What we found is that cloud is an umbrella term for many services, including SaaS and virtualisation -- anything but traditional computing behind the walls of your own data centre. If you're worried about being behind the cloud curve, don't be.

Spinning the Hype Cycle

CIOs recognise this latest hype cycle all too well. When client-server computing was all the early-90s' rage, every vendor slapped the term onto its marketing pitch whether it fit or not. Then it was data warehousing lining up to provide a single view of all your customers at the touch of a button. Next came ERP systems intended to replace the disparate best-of-breed software across business operations.