Ah, I was referring to the issue on the use of use namespace or using directives, not that there is not other bad practice.
Secondly, you said, "one more bad practice" which implies there is a different bad practice being taught in the book. I'm just wondering what you think that is. Presumably it has something to do with this thread, otherwise you wouldn't have made that post here, but I don't see anything in this thread that the book teaches that is bad practice. The only possible choice would be the use of the std:: prefix, which I'd say is actually good practice, but at worst is a style choice.