One of the features that took me by surprise is the ability to view data directly from a shared dataset. This feature is called Data Preview, and is available to anyone who has permission to view the dataset and the security at the data source works out. I’m not sure how often shared datasets have been used in previous versions of SSRS. They were not actually needed in many cases, and I generally recommended them for datasets that would be frequently reused such as common parameter lists. This advice will have to change with 2016, because shared datasets are required for the new KPI reports and Mobile Reports. Stored credentials will be used in the data sources in many cases, because Kerberos delegation is not supported yet with Mobile Reports.
This is a potential data leakage scenario, so if you have potentially sensitive data sets, you’ll want to read this post.