Sex has been a mainstream media topic even when sex was taboo during more ignorant times. By the time Marilyn Manroe came around, it was wide-spread and there was no stopping it. I think 50 Shades of Grey made reading about sex more common though, and it has started a trend.
"Sex sells," has been a marketing mantra for generations and both television shows and film have proven that even without selling a product, the including of sex in the media both mainstream and in exclusive content has been in existence since before the invention of television itself. Although the novel ’50 Shades of Gray’ has brought the concept of dominant to submissive sexual relationships to mainstream attention in a more heightened way, sexuality has always been a part of mainstream media. Women onscreen (commercials, television, and film) have been made to look appealing since the earliest days of advertising; appealing not just to be attractive as a human being, but to be attractive as a sexual object or something that could bring ‘pleasure’ which is associated in a basest of senses as sex by the human psyche. From commercials that sold soft drinks using supermodels in slow motion drinking a beverage in an unnecessarily sensual fashion to modern films that incorporate explicit scenes and language, sexuality has been a mainstream issue and icon long before the novel and will continue to be long afterward.
It is too late for sex to be made popular by a single item. Sexy models, cars, and lifestyles have been at the forefront of culture for quite some time now. Looking at books, magazines, and music there has been plenty of talk about sexual subjects. This book is hardly anything new.
No, 50 Shades of Grey did not make sex a mainstream media topic, because sex has been a mainstream media topic since before 50 shades of Grey even existed. Sex has been the media's selling point as soon as there was photography. It easily dates back until the 1920s if not earlier.
I don't think it made sex a mainstream topic. Not everyone even read the book. Plus sex was already was a mainstream topic. It was not the book that made sex a topic everyone already knew about it before the book and lots of people still talked about sex before the book and still will long after its not popular anymore.