An article of footwear, comprising: an upper; and a sole structure engaged with the upper, wherein the sole structure includes: a polymeric foam member for supporting an entire plantar surface of a wearer's foot, wherein the polymeric foam member includes a foam material having a density of less than 0.25 g/cm 3, and a protective member engaged with the polymeric foam member to cover at least 60% of a surface area of a bottom surface of the polymeric foam member, wherein the protective member constitutes a web base surface with a plurality of traction elements extending downward from the web base surface, wherein the web base surface is perforated in the forefoot area between some of the traction elements, and wherein a thickness of a majority of the web base surface at locations between the plurality of traction elements is less than 2 mm thick, wherein an outer edge of the polymeric foam member includes a first billows structure that extends around a rear heel area of the sole structure; and wherein the outer edge of the polymeric foam member includes a second billows structure that extends along a side of the sole structure, the first billows structure and the second billows structure being completely separated from one another by a smooth area of the same polymeric foam member. an upper; and a sole structure engaged with the upper, wherein the sole structure includes: a polymeric foam member for supporting an entire plantar surface of a wearer's foot, wherein the polymeric foam member includes a foam material having a density of less than 0.25 g/cm 3, and a protective member engaged with the polymeric foam member to cover at least 60% of a surface area of a bottom surface of the polymeric foam member, wherein the protective member constitutes a web base surface with a plurality of traction elements extending downward from the web base surface, wherein the web base surface is perforated in the forefoot area between some of the traction elements, and wherein a thickness of a majority of the web base surface at locations between the plurality of traction elements is less than 2 mm thick, wherein an outer edge of the polymeric foam member includes a first billows structure that extends around a rear heel area of the sole structure; and wherein the outer edge of the polymeric foam member includes a second billows structure that extends along a side of the sole structure, the first billows structure and the second billows structure being completely separated from one another by a smooth area of the same polymeric foam member. a polymeric foam member for supporting an entire plantar surface of a wearer's foot, wherein the polymeric foam member includes a foam material having a density of less than 0.25 g/cm 3, and a protective member engaged with the polymeric foam member to cover at least 60% of a surface area of a bottom surface of the polymeric foam member, wherein the protective member constitutes a web base surface with a plurality of traction elements extending downward from the web base surface, wherein the web base surface is perforated in the forefoot area between some of the traction elements, and wherein a thickness of a majority of the web base surface at locations between the plurality of traction elements is less than 2 mm thick, wherein an outer edge of the polymeric foam member includes a first billows structure that extends around a rear heel area of the sole structure; and wherein the outer edge of the polymeric foam member includes a second billows structure that extends along a side of the sole structure, the first billows structure and the second billows structure being completely separated from one another by a smooth area of the same polymeric foam member.