1. A computer-implemented method comprising: receiving, from a customer computer system utilized by a customer of a computing resource service provider, a request to instantiate a virtual machine instance, the request specifying a set of preferences for placement of the virtual machine instance, wherein the set of preferences is evaluated based at least in part on a set of other virtual machine instance placements of the customer; identifying a subset of data zones of a plurality of data zones where the set of other virtual machine instances of the customer are operating, the plurality of data zones being partitions of a set of data centers of the computing resource service provider and individual data zones of the plurality of data zones comprising a plurality of computing devices for instantiation of virtual machine instances; utilizing the specified set of preferences and the identified subset of data zones to generate an ordering for the plurality of data zones; selecting a data zone based at least in part on the ordering; instantiating the virtual machine instance onto a computing device within the selected data zone; receiving a new set of preferences; performing an evaluation of the new set of preferences based at least in part on a current placement of virtual machine instances to generate a new ordering for the plurality of data zones; and in response to the evaluation, terminating and re-launching the virtual machine instance on a computing device within a different data zone than the selected data zone based at least in part on the new ordering.