How should "The Cloud" be capitalized?

John went into the city to deposit his money in the bank

We wouldn't say 'the Bank', as we don't mean one singular bank, rather a specific but unnamed bank.

I'd use 'the cloud' in a similar way — it takes the definite article, as you'll be referring to a particular cloud, but there's an ever growing number of public or private networks available that can all be referred to as 'the cloud'.

If you're looking for a collective noun, I'd stick with cloud computing.

Edit: Just to expand on your original post Steve, I'd definitely go with #2, 'the cloud' in this case; precisely because there isn't 'one & only cloud'. When you're using cloud computing in this context, what you're saying is that you're moving systems away from a physical server room in a particular building.

They won't however be distributed throughout every computer on the internet. Instead they'll be hosted in a shared, distributed networked. This could either be privately held with software like Cloud Foundary, or hosted by a company like Amazon or Rackspace.

These are all distinct options though, each which could be referred to as 'the cloud' individually, but when spoken about together wouldn't become 'the Cloud'.

The Internet, like the Universe, is a single entity. Absent firewalls or other impediments one can input an IP address at any point in the Internet and communicate with that uniquely-identified endpoint.

"The cloud", on the other hand, is merely a concept, where data is stored "out there" rather than local to the user. What "the cloud" consists of is left to the individual service provider, and there are multiple "clouds" -- it is not a single entity (even though the marketing types like to pretend that it is).

When one says "the cloud", whether or not "cloud" is capitalized, it does not identify a specific entity, and what is "the cloud" to one user may be totally unknown and inaccessible to another. But there is only one Internet.

It might be analogous to how we use the word sea.

"We threw it in the sea." (generic) "We uploaded it to the cloud." (generic) "We threw it in the Red Sea." (specific, proper noun) "We uploaded it to the Cloud Foundry." (specific, proper noun)

The generic "cloud" is a vague noun that refers to a wide range of places of places on the Internet/internet. Like "the mountains," "the sea," "the city," "the beach," and "the country," it should be lowercased. Those words are only capitalized when they are part of a longer proper noun--Rockaway Beach, New York City, Rocky Mountains, etc.

I went to the mountains last summer, but I'm going to the beach next summer. I'm from the country, but I moved to the city when I turned 25. We moved our data to the cloud.