Just found some interesting statistics from past DV lotteries.
"In DV-2011 program record number of entrants - 86.83% Nigerian entrants and 86.45% Bangladeshi entrants were disqualified during selection process because of illegitimate entries."
Countries with High Fraud Level (percent of entries which are illegitimate and therefore disqualified during selection process) :
Africa = Nigeria 82.77%, Egypt 70.54% Ethiopia 68.57%, Sierra Leone 46.21%, Sudan 30.94%, Ghana 24.68%, Guinea 23.81%, Liberia 17.93%, Cameroon 11.64%
Europe = Ukraine 71.91%
Asia = Bangladesh 78.95%
The highest chance to get a visa per winner in DV-2009 was Nepal, Asia (85.4%) and the lowest was Senegal, Africa (14.05%)