I roleplayed in Yahoo chat rooms for several years, from the time I was 13 or so. It was certainly long enough to have seen every fantasy cliche ever. I stumbled across a picture of a boy with dog ears and a dog tail on a random Google image search (which had nothing to do with wolves or boys or random animal parts, in case you were wondering), and it reminded me of the bajillion nekos and kitsunes and anthros and what the hell evers that wandered around in chat. Naturally, I thought too much about it and had to write it down. My thoughts are not fully formed on this, so pardon me while I ramble.
I've never understood the appeal of having a character with animal parts or a ten-foot-long sword or blood-red eyes or bat wings or whatever, other than looking/seeming badass, which I guess is the whole point. To me, they're unnecessary conceits. They never contribute anything to the character or the story, so why have them?
Granted, you don't often see stupid extremes in published UF or fantasy novels, but there are still some unnecessary conceits that get under my skin. The Badass Chick Who Can Fight in Heels and Still Look Fabulous is one of the more recent and infuriating ones, but that's a rant for another time. I'm talking things like the supernatural + pop culture. Zombies, vampires and werewolves occupying "cool" positions like radio jockeys or fashionistas or celebrities. I blame fucking Anne Rice for the rockstar vampire thing, and True Blood for bringing about the popularization of this conceit. I'm sure there's some parodic message about society and the supernatural to be found in the trend, but frankly, it annoys me too much to think hard about it. I'm not sure why, except that I have pretty much zero interest in Top-40 pop culture. I find it shallow and annoying, and adding the supernatural to it doesn't suddenly make it interesting.
There seems to be a long-running trend of doing things just because you can, especially in UF. Example: the hero collects unusual, never-before-seen powers until s/he becomes a Sue, and then the author throws in some equally weird "consequences" or "flaws" from being superpowered. Yeah, I'm looking at you, Anita Blake. I'm sure needing to have sex a lot is a real burden. Or the world contains every creature to ever appear in the D&D monster manual, and they dogpile on the protagonist nonstop. As much as I enjoy The Dresden Files, that drives me nuts.
And because I can apply pretty much every one of my UF pet peeves to this series, I'm going to pick on Rachel Vincent's Werecat books. First: the protagonist's name is Faythe. Good God, seriously? Second: At the beginning of the first book, Faythe is an English literature grad student. This never appears again. This is fairly minor compared to the third point, which is the scarcity of female werecats as it applies to Faythe. Apparently, because females are rare, they Must Be Sheltered And Protected and are Obligated to settle down, marry and have babies. Vincent tries to create a really bizarre pseudo-feminist conceit in creating this aspect of the world, and in my view, it succeeds in doing nothing more than being only halfway relevant. Its purpose, I suppose, is to make Faythe seem like A Rebel Against Her Oppressive Society like early feminists. What it makes her seem like is a stupid bitch. Yup, I went there. Faythe's education and Oppressive Society serve as little more than either place settings or convenient complications, with no real purpose other than to seem like something hip and progressive.
Before I get too far into that rant, because I could go on all day, I'll turn to the real tragedy of a lot of amateur fantasy: when magic itself becomes a conceit. It happens. It's flashy. People are cool if they can do it. But it's the worst kind of gratuitous literary special effect. It has zero bearing on the world itself. It might serve as a plot point (mostly for the protagonist, who is usually the one with the magical powers and is either ostracized or heroized because of it), but it doesn't affect anyone else. It doesn't exist as part of the world. If you have something that can be as pervasive as magic, why not have it affect societies, environments, governments--people's daily lives? Not everyone has to be conscious of it (in UF, for example, a line is often drawn between People Who Know About Magic, which are usually supernatural people and those who happen to hang around supernaturals, and those who aren't, who are the ignorant mundanes), but a sensitive, subtle narrative should take pains to show how it affects people in general. How could something like magic not affect the world it exists in? How could super-powered magical/supernatural beings not affect, intentionally or unintentionally, the environments they interact with? I guess this is something the annoying pop culture supernatural stuff is trying to get at--making supernaturals pervasive rather than isolated.
I guess what I'm trying to get at is that if magic doesn't affect your world and everything in it, there's no point in having it. Yeah, it would be cool to have your character pull out some badass trick like calling lightning, but honestly, who cares if he does when there's no bearing on anything? And really, personal consequences or benefits of using magic, while a step in the right direction, are not the be-all end-all, and they can end up a conceit as well. Don't look for a reason for your character to be persecuted or adored. It's patronizing.
I think a lot of these conceits stem from concern with making characters Cool. Want to add some Coolness? Add some badass powers, magical or otherwise. Don't, like, give them an interesting personality or anything. Who cares about that? Just add some dog ears and a tail. People will either think he's adorable or they'll think he's a freak, and either can work in your favor.