I'm not aware of any specific well - known 'Cunnilingus Teacher Story' in mainstream literature. There could be some very niche or inappropriate self - published works with such a title, but it's not something that is commonly part of the literary canon.
One of the main ethical issues is the objectification. It reduces characters to just sexual objects. Also, it can make the readers uncomfortable if they come across it accidentally as it contains explicit sexual content.
It depends. The market for porno fiction is quite niche and often faces legal and ethical restrictions. So, in general, it's not a mainstream area that sells well.
The number of people watching porno stories is difficult to determine precisely. It could be influenced by factors such as the accessibility of the content, marketing efforts, and cultural differences.