Yes that is some thing very serious and they do crime far away in different land and loot money in other country, they don't have cyber crime cell effective like India and other developing countries, I have also come across some South African countries and one from Uganda. They do just because they don't have PERFECT LAWS.
There are quite a few internet scams by Nigerians. Nigeria is basically an anarchy, bribery will get you out of anything illegal, or just plain get you anything you want. Take these scams seriously, if you fall for one, the consequences of trying to get your money back can be severe. On a TV special I saw a number of years ago, they talked about a man who went to Nigeria to get his money back and wound up dead. If it sound too good to be true, it probably is.