The reason most think emailing passwords is bad, is because someone might be eaves dropping on the conversation.
The real reason is, that its very hard to authenticate the request. Is it really your mate on skype or on email ? or someone that has gained access to his PC, and now trying to get more passwords.
This is called social engineering, its when someone poses as a friend, gains your confidence, and gets passwords.
This shows the case in point – one hack, leads to email hack, leads to the main server being hacked via an email password request …. ouch !!!!
I suggest, you talk to the person on the phone (if you know their voice well), or video skype them. Authenticate the request, and then read out the password.
Passwords left in email, or in skype histories, isn’t too smart either.