To the author of this post:
http://www.joelonsoftware.com/articles/Unicode.html
And btw, here there is a loss since all character sets are not fully covered even in UTF-16 (iirc). I am trying to recall- maybe Matz gave a details reply somewhere on the net.
If they aren't covered in UTF-16, they wouldn't be covered in UTF-8 or UCS-4 either. All modern Unicode encodings (i.e. not UCS-2) can encode exactly the same data.
I'd be curious to know which character sets Unicode doesn't cover yet a different encoding system does.