Actually, adult online industry is the biggest. And being the biggest, makes it the most competitive online industry in the world, which means the best.
The adult online industry was the driving force of the internet. They exploited the need for privacy combined with the other human needs, to make huge profits. Indeed, some products are more prone to be sold online than others and this category for sure is the king.
In terms of e-marketing, most of the novelties appear here, in the adult industry: Excellent ideas to boost conversion. So, even it sound not very political correct, I recommend those that want to learn e-marketing to learn from there :). This way, they will have an excuse 😛