Christian Cachin and I published an overview on trusted clouds at IEEE Spektrum:
Christian Cachin, Matthias Schunter: A Cloud You Can Trust –
How to ensure that cloud computing’s problems—data breaches, leaks, service outages—don’t obscure its virtues, IEEE Spektrum, December 2011, pp 28-51.
Read it online at
http://spectrum.ieee.org/computing/networks/a-cloud-you-can-trust/0