Our brains are biochemically hard-wired to recognise familiar patterns almost instantaneously. A staggering amount of parallel processing goes into this, making the human brain extremely efficient at pattern recognition.
This skill is a survival instinct. Anything that is not like us is a possible threat. When you're in a book store, sneaking through the aisles, sniffing the air, hunting down that perfect new book to knock on the spine and drag back to your reading cave (complete with leather pitted chairs, banker's lamp and smoking jacket), there are a lot of possible kills to be made. Hundreds. Thousands. You need a method to quickly sort out the areas that most interest you. Book covers are one. Genre sections are another.
Genre classification as a subject for discussion heats up every so often around the net, and it's happening again. I think it's worth discussing, if only to remind us that the labels we attach to things are not the things themselves. And that snobbery is an attribute to be looked down upon.
If you're all not absolutely spent from the heated battles out there, please do chime in over here. But only if you think I'm actually making a point. I mean, I've barely slept.