1. A method for efficiently deploying and managing configurable virtual server instances in a hosted virtual server service, the method comprising: a. receiving from a user an identification of a policy to be associated with a virtual server configuration and to be used for deciding when to instantiate or destroy virtual server instances corresponding to the configuration; b. invoking, by a virtual server manager, the policy; c. retrieving periodically, by the virtual server manager, a result from the policy; and d. transmitting, by the virtual server manager to a virtual hosting service, instructions to instantiate or destroy a virtual server instance corresponding to the configuration responsive to the retrieved result.