In a recent article on Ragged Cloth Cafe (well worth reading & thinking about! http://junomain.wordpress.com/2007/10/31/interpreting-art-chap-6-interpretation-and-medium-photography/) Jeanne Beck posits the question: "Are there attributes that are as unique to textiles as selectivity, instantaneity and credibility are to photography and if so, what might those attributes be?"
I guess that the attribute that to me makes quilts unique as an art form is softnes/flexibility. Not softness as in "comfort", with its implications of warmth and caring, but the tactile experience of the quilt's traditional medium of fabric. Fabric is soft to the touch - even relatively scratchy fabric - and flexible in the hands of the maker. You can stretch it a little if you need to to make it work. Its edges won't scratch or gouge or splinter. It has give and ease. You can fold it, scrunch it, drape it over the back of your chair, spread it on top of whatever mess of random items might lie beneath. Even in the more cutting edge art quilts (ha! see, that's what I mean - cutting edge meaning literally "sharp") that incorporate numerous materials and elements other than fabric and thread, I still think of a quilt as being essentially soft, flexible, bendable, sometimes even limp.
This is an attribute that perhaps is experienced more by the maker than the viewer. I do fabric, I don't do steel beams. Hell, I don't even do rust, though I see that it's the hottest thing going right now. In the eyes of the viewer, I think people still do associate quilts, even "art quilts", as being made of fabric, and I think, though I can't really know because I can no longer see these things with the eyes of a non-maker, that this quality of softness and flexibility is still part of the perception of what makes an art quilt a quilt as well as a work of art.
For me, coming from a background of sewing, embroidery, weaving, and other skills working with fiber, I naturally gravitate to the medium I am most comfortable working with. I don't do hard-edged things - wood, metal, things that don't give, or that your can't fudge by "easing" a little here or there. I have ventured into mosaic work, the one exception to my otherwise soft-core endeavours, but it hardly counts because of the spaces between the bits of glass - plenty of fudging-room there! And mosaic work is essentially piecing & patchwork done in glass. Similar design elements, different medium, different feel. More cuts & slivers. Lots more difficult to be accurate. And I don't think I could enter a pieced glass mosaic into an art quilt show, even if I did contrive to have it meet the "three layers bound together by stitching" rule.
Lots to think about with this question, though. What do others have to say?