To get to the point, I gave a presentation at the Informa Cloud Mobility event in Amsterdam in September entitled "Dark Clouds and Rainy Days, the Bad Side of Cloud Computing", which I've uploaded to slideshare for people to have a look at and comment on. I should say that, as with a lot of things in the technology world, things move quickly and events have superseded a couple of things in the slides. It's a pretty negative slideset, interspersed with some lolcatz, but the idea of the presentation was to give an alternative view to the conference and to get people thinking. The attendees and presenters struggled even to define "cloud"; a marketing term, which is part of the problem of this topic.
For those of you who really need proper cloud security, you can buy a cloud security umbrella from my shop. :-)
Dark Clouds and Rainy Days, the Bad Side of Cloud Computing