To boldly go ...
I sense lots of BOFHs worried about their jobs.
Whether your data is stored somewhere on the Internet or not, most businesses are already stuffed if they lose their connectivity. Even if your data is local, if your Internet connectivity fails you can't take or place orders, can't send or receive emails, and increasingly can't even get on your (VoIP) phone. Most business is already dependent on the cloud (or whatever you want to call it) whether they like it or not.
SaaS is already happening as will cloud storage. SLA, reliability, security, and regulatory compliance issues are either being dealt with or will be dealt with over the next year or two. There will be enterprise class storage service providers, probably delivered by IBM or EMC or Sun, as well as the consumer services delivered by the likes of Amazon and Microsoft.
If you don't want to be dependent on a single storage provider, then use several. That's the beauty of it.
In five years, any business who is not using SaaS and cloud storage as part of its IT mix will be seriously uncompetitive. The cost advantages are just way to compelling.
I hate fads and hype. I hated dot com and I hate Web 2.0 BUT cloud computing, although I don't like the name, will transform the way IT is delivered. It's not new technology, it's just a new way of delivering old things.
I bet that when factory owners told their in house technicians that they were going to scrap their local generators and buy electricity from the national grid the techs told them they were mad. Cries of "But what if the power station fails, or the power cables are damaged, or the local substation blows up" must have been heard up and down the country.