Wikipedia describes the program as follows:
"The Diversity Immigrant Visa program is a United States congressionally-mandated lottery program for receiving a United States Permanent Resident Card. It is also known as the Green Card Lottery."However, several people have contacted us after receiving emails allegedly from the US State Department saying things like:
This is a scam. Firstly they want money up front, in these cases over $800. It then becomes unreal. The email offers you free accommodation, health care, education and a job. And guess what? They want to be paid using Western Union.
Congratulations ! You are among those randomly selected and registered for further consideration in the diversity immigrant program. Selection guarantees that you will receive a United States Permanent Resident Card(also known as Green Card or Diversity Visa)
You can see warnings from the US State Department, the Federal Trade Commission, Wikipedia (look at the "Frauds and scams" section) and Consumer Fraud Reporting.