Alma 3:4
I remember finding it interesting that the Lord does not always have to mark those who are against Him because they often choose to mark themselves. Even today people mark themselves by where they wear an earring or what tattoos they have or merely the clothes they wear. Another common practice is to mark your car with bumper stickers and logos and decals to show your affiliations, etc. The real strategy of Satan is to have his followers distinguish themselves and then work together to force social acceptance of both the mark and its associated evil.