Plenty of water-cooler chatter yesterday about the amount of space the Times gave the topic of shoe-buying as  recession Guilty Pleasure. The whole business seemed a tad frothy to me. Women, in fact, are buying all kinds of accessories (belts, scarves, costume, reasonably priced jewelry)  at a healthy clip — not just shoes. Whether they know it or not, they’re honoring a precept that pops up now and then on apparel blogs: the 70-30 Rule. The 70-30 holds that a hard-times fashionista should undertake an inventory-count when surveying her closet, and that 70 percent of its contents should be “true-and-true” items that don’t go out of style (white shirts, jeans, sweaters, etc.) and 30 percent new or nearly new trend-right items that perk up the tried-and-true and keep the fashionista’s mood buoyant as she fends off the advancing symptoms of frugal fatigue. That’s where shoes (and accessories, etc.) come in. That and the fact that shoes do have a way of wearing out.