The cloud: It's up there, high above, subconsciously suggesting that the sky's the limit. It's an intangible fluffy white entity, beyond our reach.
Its icon is usually a two-year-old's artistic impression of the phenomenon of precipitation; a squiggly polygon with giant lettering denoting "Cloud" right in the centre.
On my desk there is a Virgin Media magazine, entitled Practical Cloud, that has used the image of a typical desktop computer floating away underneath a giant red balloon with the company's logo emblazoned on the side that suggests data will be lifted into the sky and dispersed into a virtual realm, safe for eternity.
Of course, that's not entirely true. It is not floating. It is sitting on a server somewhere.
Talking with industry professionals in Rome at last week's NetEvents, the consensus seemed to be that the industry is not quite there yet, and has so far not delivered on the hype. Some of the foundations are in place, but the cloud is not unlimited, and not as spread out as we're led to believe.
Today, if you want to rent a few servers with more than 16 cores each and a wad of storage space for four days to do some data mining, you can't. The cloud is restricted by contracts, by capacity, and by bandwidth.
So what exactly is the cloud meant to be?
The current National Institute of Standards and Technology (NIST) definition has five simple, but essential, characteristics.
1. It has to be on demand, self service. If in the middle of the night I decide that I want to set up a Web server for a week, so I can host a site that details a dream I just had about flying sheep, I should be able to allocate the relevant resources without any human interaction.
2. Broad network access. That means anywhere. On the train, using a smartphone; sitting on a beanbag chair in the office tapping away on a tablet; or upright at my desk.
3. Resource pooling. Applications should be able to fire out to multiple users dynamically. I don't care if my data is coming from Iceland, the surface of Mars, or a combination of the two and I shouldn't ever need to, unless I'm getting latency issues. It should just get to me.
4. Rapid elasticity. The resources should shift and fluctuate like the ocean, except the tides are controlled by user demand rather than the moon.
5. And finally, measured service. It should all be automatically optimised, monitored, and reported. That way I know how much money I'm spending on my sheep dream website.
Essentially, I shouldn't feel like I'm renting a computer that just happens to be outside my office. I should be buying processing power, memory and storage in a way that seems completely unlimited; that will survive if a construction company accidentally chops through a copper line with a shovel; that can just exist whenever I have a passing whim, and disappear just as quickly.
That's cloud. It should be intangible; it should be a virtual world, spread across a multitude of physical entities. But it's not. Not yet at least.