It's for the ultra-high crowd; Multi-GPU setups scale better at high resolutions. If you want to run everything at the max possible resolution, with all bells and whistles + Super Sampling AA & 16xAF... well, at least for the dual/triple high-end card setups; there are more sensible applications:
If you have a motherboard that provides the needed 32 PCI-E lanes, SLI/Crossfire doesn't have to be expensive. Just get 2 9800GTs, and your performance will come close to or equal a GTX275/285, for less money.
The main drawback is the entry price; powerfull PSU for 2 cards and MB capable of full SLI/Crossfire (those 32 lanes). Your electric bill will suffer too.
I agree though that 2x GTX 295 (or even 2x GTX285) is just silly, and very costly. Just a matter of preference.
