At this point, there's been a lot of internet discussion on whether or not Katy Perry's AMA performance of "Unconditionally," in faux-geisha-get-up was racist or not. What's most annoying to me is that, well, there's a discussion. From my perspective, it's very clearly an instance of racism--as is any co-opting of other cultures' traditions and clothing as costumes. Sadly enough, a quick Google search of Katy Perry AMA shows up with results that say that people were "offended" or that her performance was "controversial." How about we call it like it is: racist. If you are treating someone else like a prop, you're not treating them like another human being. Racist. If you are calling someone a name traditionally used to denigrate their culture/race/ethnicity: racist.
While some people have acknowledged the United States' historical background and context in terms of minstrel shows and blackface, few seem to see anything wrong with doing the same with various Asian cultures. I need only to think about a couple of must-not-be-named music videos out in the past year alone, or the rampant concept of "yellow-fever" to know the veracity of that statement.
Additionally, context matters too. While one could chalk up some instances of costuming as a mistake made from lack of knowledge, Katy Perry has gone on the record about her obsession "with Japanese people." (Note: not culture. People...)
If you really want to show respect and interest in a culture, there are thousands of ways to do so besides treating them like a costume. Fictional characters are costumes. Animals are costumes. Inanimate objects are costumes. Races and cultures are not.