I don't think you can just "throw a datacenter at the problem", this is why Blue Gene exists rather than just renting Google's datacenters. Modeling cells in the body would have some advantages in parallelism due to the very real locality of the problem, but with modern parallel programming techniques things do not scale that simply. A 512-node cluster would not necessarily be able to model something 4 times as complex; as the complexity increases, the computation/communication ratio will decrease, meaning your network (especially a datacenter network) will become a bottleneck.