In the past, when I have made pumpkin pie, I have never put foil around the edge of the crust of the pie. Yesterday, I baked a pie with someone else, and they insisted that the foil was necessary to prevent the pie crust from burning. I have noticed the a lot of recipes for pies other than pumpkin (frequently covered pies like strawberry-rhubarb) explicitly call for aluminum foil on the crust.
When does a pie crust need to be covered in foil while baking?