Negative heel shoes,("Earth Shoes"), for squats?

[marklloyd]

My feet feel better when I walk in Earth Shoes than in normal shoes. If I don't have a balance problem squatting in Earth Shoes, would there be any reason not to? (My particular shoes have a very hard, inflexible sole.)

[Mark Rippetoe]

I would think that they would tend to produce a too-horizontal back angle, but since I've never seen it done I don't really know.