It should be noted that "maiden name" and "last name at birth" are not always the same. An example of when they are not the same is when an adoptive surname is used.
edit: In such cases, the "maiden name" would be entered in either the current last name field or other last name(s) field.
At WikiTree, we should think in terms of birth surname/last name at birth, not maiden name.
(my opinions)