Sure, sometimes that's what you need to do. But, other times, if you know you're sending to a trusted server, such as your own company server that you manage yourself (or people who are trusted manage), it's deemed acceptable to send passwords via email. The problem here is that facebook has introduced a new vector.

It's low grade evil; but low grade evil multiplied by millions starts looking like more serious evil. Just like low grade incompetence begins to cause serious harm when it is inflicted on millions.