Economics
Cloud offerings are not about any technical benefit, there really aren't that many, they are about economic benefit to the vendor through reductions in hosting costs and protection of long term revenue streams.
For consumers, it's about flexibility of demand, paying for what you use, rather than your peak, and transfer of capital expenditure to revenue.
If you have a consistent demand for computing a cloud is always going to be more expensive, because you are in effect renting by the minute, and placing more risk on the vendor, who will charge for that risk. The kit they provide has to host more than a single vendor, then they need to size for multiple clients peak demands, and when that resource is not in use, they still have to pay for the kit, the racking, the management tools, the networks, the power, cooling and floorspace. You can bet their cost models ensure full recovery of those costs over a relatively short time period. I can only really see cloud computing being of any value where you have a low base load with very high peaks, or can get a good deal on any base load commitment over a number of years. This doesn't tend to be how its sold though.
Oh and then there is security, client separation, and separations of duty in the ops centre do not come cheap, neither are they that easy to implement.
Ultimately Cloud computing is a financial gimmick, not a technical need, and anyway isn't it just a variation on time sharing mainframe bureaus?