Security Basics: what's the meaning of threats from unknown peoples in yahoo services? what they looking for?

[Ali asghar Toraby <aliasghar.toraby () gmail com>]

hello.
i have a question about emails that forwarded by yahoo users. emails 
that contains assertion about deleting non active yahoo users. in  this 
emails sender ask you to forward this email or yahoo off line message to 
peoples in your address book, Or send specific number to others. it is 
perfectly visible that claimant is not certified person. but i want to 
know what is their goal? why they rumor and what they gain from these gaffs?
this is a sample message that i receive yesterday.
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> > > > > > > important
> > > > > > > > > > > >> > > > > > > This is Yahoo President Jay 
Russell, I am sorry to announce that Yahoo has reached its maximum 
number of accounts two million. If you would like to keep your account 
for free send this to everyone on your list. This way we can know which 
accounts are being used and which accounts we can delete. Send this 
within 8 days and your account will remain free. Once again I am 
sincerely sorry that I have to do this. Please start sending. Jay 
Russell, Yahoo Management Renee: WHOEVER DOESN'T SEND THIS MESSAGE YOUR 
ACCOUNT WILL BE DEACTIVATED AND IT WILL COST $10.00 A MONTH TO USE IT! 
TO SEND 2 EVERYONE ON YOUR LIST, RIGHT CLICK ON YOUR GROUP DO NOT DELETE
> >

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thanks for replys