In this article Whitfield Diffie talks talks about secure cloud computing. I take comfort in knowing that he and I used to work for the same company, Sun Microsystems. There are some really smart people at Sun. The article is small and I recommend reading it. I specifically quote part of the article below as it mentions OpenBSD. I’ve been running OpenBSD for years.
TR: If a full cryptographic solution is far-off, what would a near-term solution look like?
WD: A practical solution will have several properties. It will require an overall improvement in computer security. Much of this would result from care on the part of cloud computing providers–choosing more secure operating systems such as OpenBSD and Solaris–and keeping those systems carefully configured. A security-conscious computing services provider would provision each user with its own processors, caches, and memory at any given moment and would clean house between users, reloading the operating system and zeroing all memory.
An important component of security will be the quality of the personnel operating the data centers: good security training and appropriate security vetting. A secure data center might well be administered externally, allowing a very limited group of employees physical access to the computers. The operators should not be able to access any of the customer data, even as they supervise the scheduling and provisioning of computations.