Continuing my series of posts about the big themes on this blog over the past year, I now turn to the topic of cloud computing. My views on how to implement cloud and SaaS have hardened considerably over the course of 2009. Halfway through the year, I took a conscious decision to promote multi-tenancy as the only acceptable architecture for cloud and SaaS infrastructures. You might expect that from someone who makes a living consulting for multi-tenant vendors. But I’ve deliberately chosen a hardline and controversial stance, intended as a counterpoint to the many siren voices that argue for a more hybrid approach.