Question

What is the disadvantage of the mining industry in southern and Eastern Africa

Answer 1

From outsiders perspective - not very different from disadvantages elsewhere, but bigger. 
I see two, just from general paying attention to news. 
1) resources extracted by colonists (maybe less so now, but still) and so not available to the natives of the reason, going instead to China or whoever is doing the extracting now. 
2) Tough, dirty, dangerous job to do the actual mining. Tough - wears down the miners. Dirty - will cause long term damage, like black lung. Dangerous - both mining accidents and possible danger from dealing with the greedy. 

So, to summarize, the risks are publicized to the regional people, the rewards are privatized to whoever has the power.