What can be done about nigerian scammers who have yahoo e-mail addresses?

we have recieved an e-mail from a miss monica norman, from nigeria. This person is running what is called nigerian419 scam. She claims to be ociated with a very reputable bank in nigeria (whatever) and needs to find the next of kin of a family who died in a tragic auto accident. The sum of money to be had is 6.5 million. this is clearly a scam. How can we stop these people from taking advantage of unsuspecting american citizens? What can be done to have her yahoo privledges revoked? Please help