In a large skillet, steam the beans in 1/2 inch of water until crisp-tender, about 5 minutes. Drain and refresh under cold water; pat thoroughly dry.
In the same skillet, cook the bacon over moderately high heat until crisp; drain well and crumble. Add the garlic to the drippings in the skillet and cook until softened, about 1 minute. Add the beans and half of the marjoram, season generously with pepper and toss until hot. Transfer the beans to a platter. Garnish with the walnuts, bacon and the remaining marjoram and serve.