1. A computer-implemented method comprising: receiving, by one or more configured computing systems, an indication of a group of a plurality of tasks submitted by a task requester for performance by a plurality of human task performer users via a task exchange server, the performance of the tasks of the group such that contention is possible between at least two of the task performer users if the at least two task performer users attempt to concurrently perform a single task; determining, by the one or more configured computing systems, a target quantity of multiple tasks based at least in part on a predicted level of contention between the task performer users that will occur for the target quantity of tasks; determining, by the one or more configured computing systems, a subset of the plurality of tasks to initially make available for performance by the task performer users, the subset of tasks including the determined target quantity of multiple tasks; and in response to the determining of the subset, releasing, by the one or more configured computing systems, the multiple tasks of the subset such that the released tasks are available for performance by the task performer users.