Girls only. Japan's Asahi Shimbun has an article about how Japanese arcades are banning men from sticker picture machines. Why'd they do that?
According to the piece, "A growing number of arcade operators are banning men from areas around these machines—popularly known as purikura—to protect customers, such as high school students, from men trying to sneak camera shots, steal their belongings or even pick them up."
Male-female couples are okay, but not groups of guys or single dudes. Truth is, this has been going on for a while. A long while. A long, long, long while.
However! When I interviewed the folks who manage Shibuya landmark Purikura Mecca, Japan's most famous sticker picture arcade, for Arcade Mania, I was told that male customers would not be kicked out as long as they were "well-behaved." Because, hey, they have money, too. Ironic as Purikura Mecca was the first arcade not to allow male-only purikura customers.