1. A computer-implemented method operable on a device comprising hardware including memory and at least one processor, the method comprising: (A) receiving, at a service running on said hardware, invalidation information; (B) determining whether said invalidation information relates to information currently stored on said service, and, based on said determining, (B)(1) when said invalidation information relates to information not currently stored on said service, maintaining on said service at least some of said invalidation information; and (C) using said maintained invalidation information to prevent subsequent use a version of information not currently stored on said service.