A Real-Life Horror Story...
I was recently reading the blog of an American girl heading to France to work as an English assistant in France, like I did last year. She mailed in an application for her visa, along with her passport as the visa must be placed in the passport. In short, the French consulate lost her passport, and yet they claim the American postal system lost it. The thing is that you're supposed to mail your passport by registered mail, so the American postal system probably didn't loose the passport and other documents.
Did I mention that she's supposed to leave for France in under a week?
You can check it out in her own words here.