Well its probably a cliche when people say oil is a gift and a curse all rolled up in one. This is based on the lack of positive socio economic impact that typically accompanies the discovery and exploration of oil, corruption, environmental degradation etc. So, when economic evidence buttress such views then it simply embodies the fact that oil is a curse rather than a blessing.
For example, the recent Global Competitive Index for 2012/2013 stacks up African Countries against each other to determine their competitiveness. As it turns out Oil Exporting countries in Africa faired worse than the rest as the chart below indicates. They even faired worse than low income countries in terms of competitiveness.
The chart below further discloses the problem areas Sub Saharan African Countries face in general when it comes to doing business.
As for Nigeria, below are the major problems with doing business. I bet very few will doubt this