CLOUD is a buzzword at the moment and is a pure commercial thing.
There are different types of clouds and on top of that different ways of implementing them.
What vendors ( ISP's ) do is using shared resources ( like they have been doing in the last 10 years )

My suggestion is to ask them a bit more detail and see what they can tell you that is different from what you already have.
If they are serious about Cloud computing , ask them in writing where exactly your data will be located ( live data and backup data ) , then ask what legal framework they have in place that guarantees your data availability and data privacy.
I would be surprised if their answer is anything different then " Doesn't matter, it is in the cloud, that's what it is all about isn't it ".

Simply put, the real challenge for Cloud computing is the legal framework and that is exactly the reason why major companies use private clouds, which is no different that what they have been using for the past 10 years.
Only advantage they have is that they can commission and decommission resources much faster than before, but that is only a technical solution.

My 2 cents.

Cheers ... McBie