They don't belong in any place

Reading the review for The Beautiful Country in the Onion, I was suprised to see the Vietnamese word bụi đời defined as "children of Vietnamese mothers and American soldiers". I first encountred the word ages ago on Usenet in the group soc.culture.vietnamese, where it was glossed for me as "teenage gangster". At the time, there was a rash of home invasions, robberies, and other petty crime among the Vietnamese communities of Southern California, which were attributed to teenage men of Vietnamese ancestry. The literal meaning, "dust (bụi) of life (đời)", is supposedly a reference to their rootlessness and lack of a sense of future.

I checked some dictionaries to see if, perhaps, my recollection was faulty or my informants erroneous. One of them glosses bụi đời "loose derelict; street-urchin". But if you Google "bui doi" (leaving in the diacritics gets you nothing but Vietnamese-language websites, natch), you'll find any number of webpages equating them with Amerasians. What gives?

Fortunately, rollick is one to quote her sources: "Anyone who's seen Miss Saigon should have a good idea of the significance of the words 'bui doi'[.]" I haven't, but it was easy enough to locate the lyrics:

They're called Bui-Doi
The Dust of life
Concieved [sic] in hell
And born is strife
They are the the living reminders
Of all the good we failed to do
We can't forget
Must not forget
That they are all
Our children too

This still doesn't answer the question where the authors of Miss Saigon got their definition of bụi đời, though. Could this be regional usage or slang? Or just a sad reflection of the diminished opportunities for mixed-race children of Vietnamese mothers?