I recently read this fascinating article about the making of the upcoming movie "Memoirs of a Geisha". Specifically, the piece discusses the difficulty of producing a work set in Japan but performed in English, with Asian actors from several different countries and with different levels of English ability. As if the communication between the American director and Asian actors were not troublesome enough, it was also necessary to teach all the actors to speak English with the same light Japanese accent.
I can only imagine the struggles faced by an actor who barely understands English to then master an accent other than his or her natural one. It would be like asking me to speak French with an Italian accent. Not only would I have to avoid making the sounds that pinpointed me as a native English speaker, but I would have to form Italian sounds that were unnatural for me, all the while speaking French, a language I barely comprehend. And lest anyone thinks that all Asian accents sound alike, this article gives an excellent example of how a Chinese speaker would pronounce "rock and roll" like "wok and woll" while a Japanese speaker would say it like "lock and loll".
Thankfully, the movie studios have the benefit of modern technology; in certain cases, consonants were spliced from an actor's dialogue in one scene to fit into a word that didn't sound right in another scene. (And I thought only musicians "cheated" like this!) It's an interesting challenge with interesting solutions, and I'm eager to see the final product.