One of the reasons why you see such variance is because batting has changed in the last 20 years. It's much easier to buy thinner batting than it was in the past. You don't need as wide of binding if the batting is thin. I don't like thin batting and typically do a 2 1/2 inch binding. If I do a fat batt or am tying the quilt, my binding is 2 3/4 inch. Some blankets and projects (such as tote bags) may use the 3 inch binding, which is more of a decorative choice than a need. For wallhangings, I use 2 1/4 inch. I think my friend uses 2 inch binding for miniatures. It is personal preference, but keep in mind that many of the quilters who are publishing books currently do a lot of very dense quilting on their quilts or use thin batting, making a 2 1/4 inch binding a better choice.