Storage-as-a-service (SaaS) companies have learned from the mistakes of their SSP predecessors. And a handful of well-established storage heavyweights, EMC Corp. and IBM Corp. to name just two, have made key SaaS acquisitions in recent years. SaaS is being driven by economic factors and IT realities that didn't exist a few years ago: an explosion of electronic data, compliance requirements, a tight rein on capital spending and stringent disaster recovery (DR) mandates, all of which are making storage services more appealing to small and large businesses.