In this modern age of free speech and foul talk, the concept of profanity is blurring. It has been for a long time, really, but that doesn't make it acceptable. You still can't stand in a public venue and start shouting expletives without risking a visit from a policeman (or psychiatrist). Likewise, schools are still generally swear-free zones, and that isn't such a bad thing. Do we really want our pre-teens shouting "F___ You!" on the playground? Maybe a handful of burned out hippies might argue the point, saying "kids deserve free speech, too, man (insert joint-toking sound)." But, seriously, there's still a certain negative connotation toward the use of certain words in our language.
When it comes to "literature," there is a certain level of creative license that people tend to exercise. In the hopes of adding spice or realism to their stories, writers have the tendency to slip in the occasional swear word, and that's okay in some circumstances. However, I've encountered some really good tales that would be perfectly PG if not for a handful of F-bombs and other shitty slang tossed into the mix. Yes, sometimes these words add emphasis or an element of style, though in others the words just seem to be stuck there for shock effect. We, as writers, should be cautious whenever we use such foul language, and make sure it is absolutely necessary and that we're willing to cut ourselves off from a certain reading demographic.
In my own writing, I have ended up censoring my characters to a certain extent. While I'm not afraid to throw words that are acceptable on broadcast television or radio, I tend to avoid uses of the more extreme and offensive four-letter words. That isn't to say I never speak said words in real life (I must admit, I curse more than is polite, though I'm working on that), but when it comes to the type of fantastic stories I write, curse words just aren't integral to the stories. Also, by limiting my profanity, I open my work up to younger and more prudish audiences (yet, I doubt my Amish readership will ever be a significant factor).
As I enter the world of publishing, I find my editing prerogative weeding out profanity, though it's not something I do lightly. Speaking to The Temporal Element specifically, most of the stories I received were free of extreme language, though there are a few instances (in particularly good stories) where I've had to censor a few words to preserve the PG-level collection I've strived to produce. Though the stories are obviously written for adults, I expect an 8th grader to be able to enjoy the anthology, as well, without parental concern over language. The curse words really weren't crucial to the stories involved, and I hope the authors in question respect my decision.
The point I'm seeking to make it this; just because a story is written for an adult audience doesn't mean we need to throw in a bunch of "adult" language. Obviously, there are gritty and erotic stories that demand such language, but your average adventure story doesn't need the characters being that real. Readers have imaginations, and they can read between the lines if they want to. On the other hand, there's no need to offend those readers who might not appreciate the salty flavor.
With that said, one of these days I might assemble a profanity-laced monstrosity of an anthology, but then such language will be appropriate.