The 6x rule works if you place your binding edge even with the edge of your batting, but that will mean putting quite a bit of the binding fabric inside the quilt. You may want to do that for wider bindings, just to provide more stuffing in the binding area. I think the reason we've gone to narrower bindings is so that they can be stuffed more tightly.
I use a 2.5" strip to create a .5" binding. I do this by cutting my batting 1/4 inch wider than the quilt top, lining my binding up with the edge of the quilt top (rather than the edge of the batting), and making a 1/4 inch seam through binding, quilt top, and batting. You could do this for a wider binding as well, but the formula would be 4x the width of the finished binding + .5 inch. Example: if you want a 1" binding, cut the binding at 4.5", cut the batting 3/4 inches wider than the quilt top, and sew 1/4 inch in on the quilt top and binding.
It will also be important to pay a lot of attention to the mitering of the corners if you do a wider binding, because they will show up more.
This method solves the problems that maride brought up, since you're still sewing a 1/4 inch seam allowance, but you aren't sewing binding over your border or blocks.