1. Kids - Little fingers can get into places they shouldn't be in.
2. Pets - Kittie likes a nice warm area to lay on..
3. Dust, Dirt, Pet Fur, Hair all love to collect on energized electrical equipment. Better stock up on canned air, or get yourself a small air compressor, cause cleaning this rig will be a weekly occurance

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My youngest child is 20, the dog is asleep on the floor most of the time, and a computer sucks in dust no matter what anyway. (filters restrict too much airflow for overclocked, multi-gpu setups)

My house is fairly dusty, no matter how much attention we pay to cleaning. I use a compressor for cleaning computers. The Antec Skeleton open frame design would cut down the time for a thorough cleaning session by two-thirds or better.

What I see as disadvantages:

It won't mitigate fan noise like conventional cases. (Sorry, you just can't create a silent computer with highly overclocked CPUs and multiple GPUs all at full load. Yeah, sure, a stock clocked machine at less than full load is a piece of cake to make quiet.)

It requires more surface area. An upright-oriented computer case, even a full tower, has a much smaller footprint.

I'd still love to have one of these skeletons. I love the concept and the visual appeal.