The way we understand it, many Chinese-Americans, at least in past generations, chose American names for their kids (and themselves) based on what sounded good. They favored names that sound like words for success, prosperity good luck and so on. This may be part of the reason for all the Vincents. And Winstons, and Winnies. Also, immigrants would often get a new name from the officials. You'd come in and say your name was Lu Xing-yu and they'd put down Louis Yu or something. (You'd be lucky if they got it that close.)

But like most things it's more complicated than just that. (http://books.google.com/books?id=sc1kf_A5AAwC&dq=Chinese+American+names&printsec=frontcover&source=bl&ots=b_2IfS42gW&sig=W53_a_xygdVElmIjEAWv98XWRQU&hl=en&ei=C6TwSd2cCJXqtQOv58z3Cg&sa=X&oi=book_result&ct=result&resnum=4#PPA13,M1)