Interestingly, the stereotype, has caused a large dent in the country's reputation (Paypal won't allow Nigerians to recieve funds) and there's a percievable reduction in the number of scammers from Nigeria. I believe many scams that claim to be Nigerian now are only taking advantage of the stereotype.
This stereotype has also made getting jobs considerably harder for sincere freelancers like me. And if I happen to find a client, I treat them like gold; I always work beyond expectation in an attempt to prove I'm not a stereotype.
It's frustrating though.