The bad thing about these labels, especially with all of the new sub-genres, is that it is limiting. One example is romantic suspense. It is categorized in romance and there is a definite stigma associated with the section for a lot of readers. Most mystery readers, while they would find a plethora of books that would interest them, would never venture into the romance section and vice versa.
For those who are curious, labels and sub-genres within the mystery section include, hard-boiled, medium-boiled, cozy, police procedural, noir ... the list goes on and on. The implication is that this book is of a particular style and so if you like others in the sub-genre you'll like this one. As a bookseller, this is a very important tool. There is no possible way that I could ever have read everything we had to choose from and so if I knew that a customer liked something in particular and I knew of other authors that wrote that way, I could easily point them to some suggestions.
The latest sub-genre that has been bleeding into mystery is urban fantasy. I love this label and author Jeanne Stein agrees. It implies that there is a strong contemporary fantasy element that is blended with another genre, in a lot of cases mystery. This is, I believe, thanks in part to Buffy the Vampire Slayer. It's fun and it opens up a whole new element in the genre, detectives and crime solvers who are not bound by real world constraints.
The label that probably bothers authors the most is the cozy label. I like cozies, for the most part. They're light and easy reads. In fact, I cut my teeth on cozies since they all came off my grandmother's shelf and she was censoring me in a way. Sadly, cozy authors I think get a lot of flack from non-cozy readers. They also catch it from the publishers who, for the most part, have this idea that a cozy has to be family friendly reading. In other words, most would probably get a PG, possibly PG-13 rating. Even prudish me doesn't agree with this, but I understand it.
There is no easy solution to this issue. One author spoke of a bookstore she had once visited where all fiction was shelved together. She also said that she suspected the store was no longer open. I realize that labeling is a marketing scheme but that's simply the nature of the business as it is now. You want to walk into a store and head to a section and browse books that you know you will most likely enjoy. The fact of the matter is this, most readers have a certain comfort zone and most will never venture out of this zone. I am not one of those readers and so I know that these people are probably missing out on some great books. This is where you hope the bookseller will come in and help you out. Sadly, this is not likely to be the case in many chains anymore - there are some, don't get me wrong, but we are few and far between.