I agree that SLI setups should have been included, but that would also involve a cross-platform setup that might skew the numbers slightly. Even so, it would have been nice to let us know where things stand.
However, I believe what is really being shown off here is the scaling ability ATI is pushing for. Since ATI is apparently shooting for multi-GPU setups on a grander scale than the HD3870X2, it's encouraging to know that they're making good headway in that department. We've got multi-core CPU's, and it's only a matter of time before we get multi-core GPU's as well.