Tear frisee into bite-size pieces and put in a large bowl. If using slab bacon, cut lengthwise into 1/4-inch-thick slices. Cut bacon slices crosswise into 1/4-inch-thick sticks (lardons).
In a heavy skillet cook bacon over moderate heat, stirring occasionally, until golden and remove skillet from heat.
Have ready another skillet with 1-inch warm water. Half-fill a 4-quart saucepan with water and stir in white vinegar. Bring liquid to a bare simmer. Break each egg into a teacup. Slide 1 egg into simmering liquid and immediately push white around yolk with a slotted spoon, moving egg gently. (Egg will become oval, with yolk completely covered by white.) Add remaining 3 eggs in same manner. Simmer eggs about 1 1/2 minutes for runny yolks to about 3 minutes for firm yolks. (Serving this salad with runny, not fully cooked yolks may be of concern if there is a problem with salmonella in your area.) Immediately transfer eggs to skillet of warm water. Reheat bacon in its skillet over moderate heat. Add shallot and cook, stirring, 1 minute. Add red-wine vinegar and boil 5 seconds. Immediately pour hot dressing over frisee and toss with salt and pepper to taste. Divide salad among 4 plates and top with drained poached eggs. Season eggs with salt and pepper and serve salad immediately.