I believe vBlock as an Architecture is geared for well designed and highly scalable Cloud implemenations where the emphasis is on "standardization". vBlock is an excellent product for scale up and scale out approach. By coupling Compute, Storage, Network, Hypervisor into a single Rack, the Rack is self becomes a "unit".
Furthermore, you get a single support group. You dont need to run to multiple vendors/partners for support. vBlock basically breaks the concept of a having a monolithic tiered SAN and Access layer Networking. Instead, you get distributed Storage and Networking in the Racks and this makes vBlock a product highly scalable.