This paper identifies and discusses trends and open issues regarding the use of trust in data-provisioning service environments, especially cloud environments. Applying a systematic review method [2], we propose a classification scheme used to provide a quantitative view of current trust solutions insisting in open issues. Finally, using analysis results, we give the general lines of an approach for improving data provisioning in multi-cloud using Service Level Agreement (SLA) and proposing the notion of multi-level trust.