in a large deep heavy skillet, melt butter over med-high heat. stir fry pancetta until it turns golden, about 5 minutes. remove from pan, drain off all fat except 1 tablespoon.
add garlic 2 tablespoons of the parsley and hot pepper flakes, stir fry for 1 minute. pour in clam juice and wine, bring to a boil, add clams, cover and steam until open, about 5 minutes, discard any that do not open.
meanwhile in a large pot of boiling salted water, cook linguine until tender but firm. drain and add to pan along with pancetta, toss to coat well.