Members of the Modern Quilt Guild are discussing this question on their blogs. Apparently it's quite a heated issue, which I was previously entirely unaware of. Admittedly, I've only been quilting since the summer so I'm probably not up on quilting controversies. I mean, who outside the quilting community would even think there was such a thing as a quilting controversy?
I believe that I am a modern quilter because I am a member of a modern society. As such, everything that I engage in is a modern activity. I don't harvest my own cotton, weave cloth, then stitch it together. I don't make quilts using scraps of fabric that I have saved from sewing my own clothes, or cut from those clothes when they've worn out. I don't hand sew by candle light after I've finished cooking dinner on my wood-burning stove and washing dishes in a dishpan.
However, everything that I do as a quilter builds on things that my quilting ancestors did. I cut out pieces of cotton fabric and sew it together with thread. At a very basic level, that's what quilting is, so that makes me a traditional quilter. I use a rotary cutter, mat, an iron that produces its own steam, and an electricity-powered sewing machine. That makes me a modern quilter.
I think the choice to see oneself as a "modern quilter" is just that - a choice. If you want to believe that you are a modern vs a traditional quilter, go ahead. But I firmly believe that these aren't two separate categories, they're just aspects of the same whole. Sir Isaac Newton said, "If I have been able to see further than others, it is because I have stood on the shoulders of giants." Whatever personal twists I bring to the art of quilting makes my quilting modern, but my modern quilting is founded on the work of generations of traditional quilters, who were also "modern quilters" in their time.