Virtual data stores may be sparsely provisioned by virtual data storage services in a manner that controls risk of implementation resource shortages. Relationships between requested data storage space size, data storage server capacity, allocated data storage space size and/or allocated data storage space utilization may be tracked on a per data store, per customer, per data storage server, and/or a per virtual data storage service basis. For each such basis, a set of constraints may be specified to control the relationships. The set of constraints may be enforced during implementation resource allocation, and by migration of data storage space portions to different implementation resources as part of a sparse provisioning load balancing. Sparse provisioning details may be made explicit to virtual data storage service customers to varying degrees including explicit, aggregate on a per customer basis, and aggregate on a per virtual data storage service basis.