It's odd how the different genes in any given artistic media form there own little communities, each with their own set of protocols. This was sparked the other day when I was listening to a program on the radio and they were interviewing a jazz writer. He's a musician as well, but he makes his primary living writing about and reviewing other jazz musicians. The part about the genre culture came into when he was talking about how, when he goes to review musicians or write about festivals or the like, he's often invited to play with the musicians. (Technically I suppose it would be "jam with" but no matter.)
This was then contrasted to when someone would write a review of a classical musician or performance, where it is very unlikely the writer would be invited to sit down and perform alongside the musicians, even if they play. (Of course, if you're a classical musician, likely you're making a better living playing than you would be writing about playing.)
There are similar things in the fiction writing community, I imagine. From what I've seen there's often an overall sense of camaraderie, with everyone defined as "writers." The only significant division I've noticed at the top level is between those who write "popular" fiction as opposed to those who write "literary" fiction. (Also often determined by those who came to the craft on their own, and those who pursued a MFA or one of those creative writing degrees.)
I suspect, however, that there are probably ins and outs among the various genre communities, things that say a gathering of horror writers might find normal (such as comparing research tidbits - the gory kind - over dinner) whereas it might be very different with a group of romance writers. ... Actually, that later might be a bit more interesting, but then again that's likely just my twisted imagination.