Update: Judging by the overwhelmingly negative reviews, this product looks good but it's crap. I definitely wouldn't consider it now.
No, you don't need a damn case for your iPhone 5—but if you have butterfingers and you must use a case, this seems to me like the only acceptable one. The SurfacePad is not only simple and elegant—complementing the iPhone's design rather than turning it into an ugly hulk or a clear-plastic-wrapped granny sofa—but also has function. And it protects your screen too, unlike 99 percent of the offensively horrible covers out there.