Mongo Aggregate Output

/* 1 */
{
    "fb" : null
}

/* 2 */
{
    "fb" : null
}

/* 3 */
{
    "fb" : null
}

/* 4 */
{
    "fb" : null
}

/* 5 */
{
    "name" : "Person Name",
    "fb" : "www.fb.com/maria.mongodb"
}

/* 6 */
{
    "name" : "Some Name",
    "fb" : "www.fb.com/some.name"
}