I spent way, way, way too much time poking around the idea of cultural appropriation after a friend linked to that Salon article about belly dancing. It seemed wrong to do a glancing fact check on it (altho I'm sort of glad I did, because one of the artifacts of tracking down that foolishness about Mark Twain making a film in 1893 was realizing that phrases like "fun fact" should raise your fact checking sensors at least as quickly as infographics) and then not address the very real issues raised in the article, and highlighted by my friend.
I've tentatively come to the following:
It's probably better to treat cultural appropriation Dos and Don'ts as a matter of etiquette and respect, than as a ethical or theoretical or philosophical construct. Etiquette is generally understood as having a certain amount of arbitrariness and situation-specificness to it (and it is recognized as evolving over time) especially compared to the other frames, and it also has built into it the idea of showing respect/treating others as one would like to be treated/etc. which is so missing from clueless idiots who attempt to construct a persona or identity out of cultural pastiche -- and those clueless idiots appear to be the dominant form of cultural appropriation that is currently offending. Discussions of cultural appropriation which attempt to draw bright lines, or elucidate clear and universal principles seem to not be as helpful as one might wish (altho those bright lines and universal principles can do a _great_ job of attracting attention and passion, which serves a valid purpose in this context).
As always, if you are attempting to deploy a characteristic you have strength in, to appear to have a characteristic you do not have strength in, Trouble Awaits. You may be very smart and able to travel the world, but if you attempt to use your cultural acquisitions abroad to make yourself seem cool, you aren't. Privilege and power relations are probably happening, and not in a way that future-you will be proud of. Alas, the whole thing is even rougher on those who are less smart and less able to travel, who attempt to adopt other cultures at home via media representations or other means. In their heads, they are being open-minded and interested in other cultures. Other people have other thoughts, probably including those they are attempting to emulate.
The pass you can get for being a fan/nerd/acolyte/wtf is dangerous and limited; it's only good as long as you don't make any demands based on it.
All that said, saying, "That's Cultural Appropriation!!!" does not make one right or righteous. Just like any other assertion, it can be valid or not. And there are some people out there trying to police this stuff that aren't necessarily making enough effort to get it right. Etiquette has a bunch of rules about _that_, too.
Finally, it is _very_ important to recognize that lots of things offend, whether that is expected or not. It's probably wrong to base any kind of value system on avoiding offending anyone at all (it's definitely foolish), but pretending one _hasn't_ offended, or trying to argue the person who is offended into not being offended is even more wrong.
Or as my husband would say, we should try to be kind.
ETA: Oh, and if you are a WP doing some sort of POC activity like belly dancing or martial arts or cooking food that you didn't grow up with or whatever, and a POC tells you You Are Doing It Wrong, please listen politely, say thank you, and refrain from arguing. WP have apparently been behaving badly and should knock it off, and even if you in particular haven't been behaving badly, you should probably strive to raise the average.