Pegging is a sexual practice in which a woman performs anal sex on a man by penetrating the man anus with a strap-on dildo. There may be more than two participants; both group sex and gang banging can be included. Interracial pornographic films have experienced an explosion in popularity, becoming one of the fastest-growing and biggest-selling genres. Sadomasochism is practiced in isolation relatively rarely, though some masochists report biting, pinching, or even stun-gunning themselves as a prelude to, or as part of, masturbation. Depictions of male and female masturbation are common in pornography, including gay pornography. Emetophilia pornography involving vomiting and gagging. Simultaneous penetration of the mouth and either the vagina or anus. The name is a reference to gonzo journalism, in which the reporter is part of the event taking place. The genres of pornography are based on the type of activity featured and the category of participants, for example mateur pornography is a category of pornography that features models, actors or non-professionals performing without pay, or actors for whom this material is their only paid modeling work. The inside of a smotherbox is often padded to provide support for their neck and prevent their head from moving. Starting with erotic stories and woodblock prints from before the 20th century, Japanese pornography evolved into distinct subcategories with the media that in addition of pornographic videos and magazines featuring live actors, there is exist categories of pornographic manga , pornographic computer games , and pornographic anime . A celebrity may allow such a recording to surface willingly, as part of a publicity stunt. It is sometimes combined with BDSM features. This technique may include the use of a simulacrum, or artificial vagina. Animal masturbation has been observed in many species, both in the wild and in captivity. Commercialized pornography accounts for a nearly US0 billion worldwide gay teen porn industry for the production of various media and associated products and services.