Place the eggs in a medium saucepan and cover with cold water by about 1 inch. Bring to a boil, then reduce the heat to low and simmer 10 minutes. Drain the eggs and run under cold water until cool; peel, chop and set aside.
Meanwhile, put the potatoes in a large pot and cover with cold water by about 1 inch; season generously with salt. Bring to a boil, then reduce the heat to medium and simmer until just tender, about 12 minutes. Drain and let cool 5 minutes.
Cook the bacon in a large nonstick skillet over medium-high heat, stirring occasionally, until browned and crisp, about 7 minutes. Remove with a slotted spoon and drain on paper towels.
Combine the potatoes, hard-boiled eggs, bacon, scallions and celery in a large bowl. Add the dressing and toss to coat; season with salt and pepper.
Green Goddess Dressing
Combine 1/2 cup each mayonnaise and sour cream, 1/3 cup each chopped parsley and chives, and 1/4 cup chopped tarragon in a blender. Add 2 anchovy fillets, 1 minced garlic clove, 1 tablespoon capers, the juice of 1 lemon, 1/2 teaspoon kosher salt and a few grinds of pepper; puree until smooth. (Makes 1 1/2 cups.)