Soak the corn in cold water for 30 minutes or more. If necessary, use a weight to keep the ears submerged. Drain. Grill the corn over Direct Medium heat for 20 to 25 minutes, turning three or four times during grilling time. Remove from the grill and allow to cool slightly. When cool enough to handle, carefully pull back the husks and remove the silk. With a sharp knife, cut the kernels from the cobs. Set aside.
In a 9- or 10-inch skillet over medium heat, fry the bacon until the fat is rendered and the bacon is crisp, 10 to 12 minutes. Remove the bacon and set aside on paper towels to drain. Remove all but 1/3 cup of the fat from the bacon drippings in the skillet. Add the garlic and shallot and cook over medium heat until translucent, 2 to 3 minutes. Add the sherry wine vinegar and continue cooking over low heat for 3 more minutes. Set aside.
Wash the scallops and remove the small, tough side muscle. Place in a medium bowl. Add enough olive oil to lightly coat. Season with salt and pepper. Grill over Direct High heat until just opaque in the centre, 4 to 6 minutes, turning once halfway through grilling time.
In a large bowl combine the spinach leaves and dressing. Toss to evenly coat the spinach. Divide among four plates and add tomato wedges, avocado slices, corn, and scallops. Crumble a piece of bacon over each salad. Serve warm.
