In all fairness, it's a word/accusation that's thrown around so casually these days that I'm not surprised that some people feel that it's losing its value.
Anyway,
very true, same also seems to apply to 'rape' too... it is really counterproductive for people to use these words when making accusations regarding rather trivial things that don't come anywhere close to fitting the definition of the word
Again though, this term only seems to exist on the net. As someone said above, you might here someone make a jibe about a predominantly white audience at a concert or something, but that's more an observational jest then anything else. Hell, I've made that sort of joke plenty of times.
nah it seems to be a thing on US college campuses (with all the associated hypocrisy that goes along with that sort of thing)
for example the staff at one US university having no issue with a soviet themed party but all hell breaking lose when students had a Mexican themed one
the white guy with dreads video is also ridiculous, has been posted on here before and it isn't as though dreads have only come from African cultures. And also Africa is rather a large diverse place - I wonder if SJWs consider that not all black people will have had ancestors with dreads in their 'culture' either.
Halloween is a good example of the misplaced angst/silly accusations of Racism:
Example 1 - Hillary Duff and Boyfriend two white Americans dressed as a Pilgrim and Native American... seems pretty relevant to their culture/history right? Wrong it is disgusting and racist apparently.

Despite the consumes being quite respectful, realistic and not mocking anyone. There is some issue with wearing Indian war bonnets - they're awarded for bravery etc.. however he's not trying to pass himself off as an actual Indian or fool anyone - nor is it a genuine bonnet. Likewise there is a difference between dressing as a 'soldier' for Halloween, blitz themed hipster party etc.. and passing yourself off as an actual soldier - or wearing actual medals/insignia(as per Michael Jackson - though IIRC SJWs didn't take issue with that).
Example 2 - Now we have the Zuckerberg's fancy dress this year - a Jewish American man and a Chinese American woman dressed as Vikings. Did we get an outcry of 'Appropriation' from the SJWs on tinder, twitter etc.. nope (aside from some ironic comments).
Although Zuck and wife are clearly not Nordic this sort of supposed 'appropriation' seemingly doesn't account. Frankly what they're doing is as innocent as Hillary Duff and her boyfriend - they're both simply dressing up, respectably, for a bit of fun at Halloween. In neither case do the costumes attempt to mock anyone. However it seems, if the 'culture' your costume comes from has some special cupcake status in the eyes of SJWs then you're a horrible racist and if you're a celebrity and you get caught out by this then your publicist will make sure you issue a grovelling apology. If you're a student you'll potentially face disciplinary action - it is all pretty ridiculous, some US colleges have set up special helplines for students to report cultural appropriation and to offer counseling if they're traumatized by it.
Even Glastonbury has banned Indian headdress but I doubt they'll ban bands or guests from wearing coats from British military dress uniforms and regimental insignia.