ARS Technica takes a look at the top web scams of the decade, you can check it out over here. One of the more popular ones is the Nigerian scam:
The Nigerian scam. You knew this was going to top the list. Basically, you get a message from someone who identifies himself as an ex-government official in Nigeria. Could be some other country too, but Nigeria excelled early in this activity. The scammer says he has a truckload of money to get out of the country, but first needs a bank account to transfer it to (yours) and will then gladly give you a percentage of the cash for your assistance.
Amazingly, the victims of this grift are often so convinced (or perhaps blinded by greed) that they will then forward cash for "bank fees" and other bogus expenses in order to make the deal happen. Panda says these phony fees go as high as $1,000, and of course, no money is forthcoming from the scammer.
One ex-scammer says that nine or ten out of every 1,000 e-mails sent out get a response. "Then maybe 1 out of every 20 replies would lead to us getting money out of the victim in the end," he explained. Despite the efforts of the Federal Bureau of Investigation and a small army of scam baiters, this awful racket is still going strong.