“…They satisfy some basic requirements for a Grid setting [20], namely: 1) they are naturally decentralized, 2) decisions about whether to consume or provide resources are taken locally by the clients or service providers, 3) the use of currency provides incentives for service providers to contribute resources, and 4) clients have to act responsibly and cannot afford to waste resources due to their limited budget. A number of systems [1], [3], [10], [16], [26] have been built using a market mechanism to allocate the computational resources. However, all of them make the inherent assumption that a market-based approach is per se better, which is ad hoc, as the allocation depends on many factors besides demand and supply, such as communication delays, bandwidth, server speeds, etc.…”