It is in a high risk area of Africa. From a Seeking Alpha write up:
My biggest concern with Banro is the geopolitical risk of 100% exposure in the Democratic Republic of the Congo. The country has been going through a severe Civil War since 1994 (tensions have calmed down since the peak and the UN has declared peace, but the violence is ongoing) that has claimed more lives than any conflict since World War II. The DRC is also one of the world’s most corrupt countries in the world ranking seventh on the Transparency International survey for most corrupt countries.
Since its independence from Belgium, the country also has a history of nationalizing profitable mines. Some reforms have been enacted to make the country more transparent and business friendly over the past ten years. However, I am not quite sure that the government has reformed enough to maintain the safety of Banro’s assets, but most of this risk is already priced into the company.