Methods and apparatus provide for: assigning each of a plurality of
requesters to a respective one of a plurality of requester groups;
receiving tokens from a plurality of resources, where each token is an
exchange medium for permitting one of the requesters having the token to
access an associated one of the resources for a period of time; receiving
requests for the tokens from one or more of the requesters; allocating
the tokens to at least one of the respective requester groups and the
requesters thereof based on token allocation criteria; and dynamically
re-assigning one or more of the requesters among the requester groups
based on feedback information concerning at least some prior token
allocations.