Michael S. Kaplan had a blog post about this in 2005: http://blogs.msdn.com/b/michkap/archive/2005/09/17/469941.aspx?Redirected=true
In Japanese 円 is generally used for yen, in Korean 원 is generally used for won, but both the yen sign and won sign are also used. Some somewhat-Unicode Japanese or Korean fonts have Yen sign or Won sign respectively instead of backslash in part due to what Kaplan explains. Obviously things get messy when copying the backslash character from a Japanese font to a Korean font if that character has a different currency glyph in both fonts.
