1. A computer-readable storage medium having computer-executable instructions stored thereupon which, when executed by a computer, cause the computer to: store, at a service provider network, a plurality of placement strategies configured for use in influencing placement of virtual machine instances on particular hardware platforms in the service provider network; store data associated with at least one placement strategy of the plurality of placement strategies; receive, at the service provider network from a client device, a request for a placement strategy suitable for use with an identified virtual machine image; in response to receiving the request, search the data to identify a placement strategy, among the plurality of placement strategies, that is suitable for use in identifying a hardware platform in the service provider network upon which to execute the identified virtual machine image; and return, from the service provider network to the client device, the identified placement strategy in response to the request, wherein the data further comprises user-provided ratings for publishers of the plurality of placement strategies, and wherein the user-provided ratings for the publishers of the plurality of placement strategies are utilized to select the placement strategy suitable for use with the identified virtual machine image.