You'll find a majority fo the scam emails you get are from Nigeria.

The Nigerian Embassy basically blames the victims (http://www.nigeriaembassyusa.org/fraud.shtml):

Please join the CBN and the Federal Government of Nigeria to fight the criminal syndicates who play on the gullibility and greed of their 'victims' by reporting any solicitations to your local law enforcement agencies or the local International Police Organisation (Interpol).

Of course they don't seem to give ready contact information for Interpol.

It's gotten so bad now that the Nigerian Embassy in Washington DC is under attack. From their website on February 7, 2006: (http://www.nigeriaembassyusa.org/419statement2.shtml):

419 OPERATIVES IN WASHINGTON D.C. DISCLAIMER NOTICE

The Embassy of the Federal Republic of Nigeria, Washington D.C., USA would like to inform members of the public of the fraudulent activities and operation of a criminal syndicate parading itself as the "Consular-General" of Nigeria in Washington, D.C. The criminal gang is now using the address of the Embassy on its bogus letter-headed paper with dubious telephone number 202-331-4411 and fax number 202-331-4405. The Embassy believes that the gang is using the name of the Embassy and that of the Nigerian Government for the purpose of facilitating criminal overtures to unsuspecting members of the Public.

2. In the last couple of weeks, this Embassy has had to respond to numerous enquiries regarding the status of the so-called Consular or Consul-General of Nigeria in Washington. Consequently, we hereby categorically state that the Federal Government of Nigeria has not established any representative office in the United States other than this Embassy, our Permanent Mission of Nigeria to the United Nations in New York, and the Nigerian Consulates in New York and Atlanta. We also disclaim the telephone and fax numbers, as indicated above, which the fraudsters have on their bogus letter-headed stationery.

3. The Embassy has already notified the appropriate US authorities on the fraudulent activities of this criminal gang. Meanwhile members of the public are hereby advised to be wary of these criminals and to report any solicitation or overture from them to the Embassy or the Law Enforcement Authorities.

Economic Section
Embassy of Nigeria
Washington, D.C.
February 04, 2004