Have you seen this scam yet?

You receive an email sent from one of your friend's own email addresses with your friend's own email signature at the end, asking for money because of an emergency.

Here are two variations I have seen so far:

1.  How are you doing? I am sorry I didn't inform you about my traveling for a Program called Science, Health and Environmental Reporting. It is currently held in Nigeria, Sweden and Kenya. I am presently in Nigeria. It has been a very sad and bad moment for me because i got robbed on my way to the hotel where i lodged. My ID, cash and other valuables i have with me got stolen, I contacted the embassy here to help me out but it will take some time to get back to me. I urgently need your financial assistance of $2,600 to sort-out my hotel bills and get myself back home. I will really appreciate your help and i promise to pay you back immediately upon my return. Hope to hear from you soon.
 
Regards,

 2.   How are you doing? I am writing you this message with
 sorrow because of what I am going through right now. Am in a
 great sorrow written you this note, I could barely type or
 think straight right now, I hope you come to my
 aid....something very terrible is happening to me where I
 am, I seriously need help from you urgently, I had a trip
 here in West Africa {Nigeria} for a conference.
 Unfortunately for me I got robbed on my way to the hotel
 where I lodged along with my Cell phone, bag where my
 passport was and since then I have been without any money, I
 am even owing the hotel here. So I have limited access to
 emails for now, I urgently need your financial assistance.
 The total sum of money that I would need would be $2,475 to
 sort-out the bills so I can make arrangements and return
 back, I'm in a panic now, the police only asked me to
 write a statement about the incident and directed me to
 the embassy, I have spoken to the embassy here but they are
 not responding to the matter effectively, I will return the
 money back to you as soon as I get home, I am so confused
 right now. I wasn't hurt because I complied
 immediately.  I'll wait to hear from you so I can
 send the Western Union information to use in sending the
 money.
  
 Hope to hear from you soon.
    
 Sincerely,

Number 2. is obviously written in spam-ese; but Number 1 could almost pass for a native english speaker.  If the bad guys ever learn proper syntax, spelling and grammar, we will be in big trouble.  But I digress.

Evidently the spammers hack someone's into email address book, and send out an email blast looking as if it came straight from that person.

If a friend replies to that email, I would imagine the hacker has the reply rerouted to the hacker's op center, where a response goes back out telling where to wire the money.

The person whose email was hacked never knows anything happened until one of her friends says something like "Gee, I didn't know you had traveled to Nigeria, but I hope the money I wired you helped."