Amateur porn has been called one of the most profitable and long-lasting genres of pornography. In many cases, that person is also aroused by smelling body parts that have a urine scent. Partners can engage in penetrative sex, known as full swap, or choose to soft swap in which they engage only in non-penetrative sex. Accepting that Eros is not always pretty, and may involve the forbidden hentai porn or taboo - as with women pornography – forms part of the struggle with the good girl/bad girl or virgin-whore split in postmodern femininity. Twink pornography features younger performers, and usually features young men under 30 who identify as gay or bisexual. The legal status of masturbation has also varied through history and masturbation in public is illegal in most countries. Others involve partners who naturally have a significant difference in size. Cum-shot pornography features a collection of male ejaculation scenes. Such films continued to be produced but could only be distributed by underground channels. Body parts including fingers, tongue and penis may be used for anonymous oral, vaginal and/or anal intercourse. Central to the typical MILF narrative is an age-play dynamic of older women and younger lovers. In these cases, the appearance of an enlarged abdomen caused by obesity or overeating may be sufficient, or simply the suggestion of a protruding navel. The gay movies fundamental principles for the exercise of BDSM require that it should be performed with the informed consent of all involved parties. Crying pornography that features participating actors crying. This category also includes pornographic home movies. The term is a slang word that originated in the gay community and comes from the equestrian lesbian milfs term bareback, which refers to the practice of riding a horse without a saddle. Anti-pornography psychologist Ana Bridges and colleagues conducted a content analysis of best-selling heterosexual pornographic videos showing that over 96% of all scenes concluded with a male performer ejaculating onto the body of his female partner.