As far as eDiscovery goes, cloud-based computing primarily presents as a cloud-based hosting site with eDiscovery services running over the hosted data. Granted, some commentators believe that Software as a Service (SaaS) is by definition cloud-based computing because the application is delivered from the Internet. I disagree. I do not consider Web-based software delivery or browser-based applications to be clouds simply because they are delivered via Internet services.
Consider this model of a cloud-based service: a remote host uses highly scalable and virtualized computing resources to host their clients' data and also hosts eDiscovery software at the remote site. End-users access this hosted data, eDiscovery software and services from their workstations. An example of this model is CaseCentral, which hosts client data on a private cloud - i.e., a private physical infrastructure as opposed to a public cloud like Amazon S3.
Now we have an announcement from CA and Acxiom of cloud-based governance service with implications for compliance and eDiscovery. The service offers a single portal view for email management, archiving, litigation holds, search, records declaration, retention and disposition. The service impacts both Legal and IT, which is good. Their eDiscovery tasks are becoming inextricably entwined and I'm glad to see hosting services cement their teamwork.
Long-time infrastructure provider Acxiom is handling the computing environment while CA delivers the information governance. I hesitate to say that CA is a full-blown eDiscovery software provider although they certainly have capabilities in the field. Their approach marries the first few stages of the eDiscovery workflow, where good information management feeds in to cost-effective identification and collection. Attorneys will be most concerned with preservation, processing, analysis and review; but search and collection impacts both them and IT. (Which is why the early stages benefit from cross-functional IT/Legal teams.)