Disclaimer - this is purely based on a bit of prior knowledge and augmented with some more research, I've never been to subsaharan Africa and don't really plan to ever wild camp there!
Wild camping around that area verges along the more extreme side of wild camping - some may say it's madness, and there's obviously much, much more risk than wild camping in your average field or an accessible location of countryside. But if you are doing it I'd definitely take a tent, at least that way you've got some element of protection if nothing else.
Risks? Well first off you've got venomous snakes. Subsaharan Africa is crawling with them and while some varieties won't tend to strike unless they really feel threatened, others (Black Mamba) are both quick to strike and kill basically every time unless antivenom is administered in time. This is a very real risk, a quick search reveals it's a pretty big problem in this area and definitely not just confined to parks. Then you've got other nasties such as scorpions and spiders, while generally they're not as venemous as snakes some varieties can still kill you, and at the least if you get caught out it'll land you in intense pain and possibly cause you to be disoriented for a while.
Other than animals, you've also got people - an aspect of survival often forgotten about. Parts of it can be corrupt and especially at borders, you may have critical supplies stolen on your travels and have no sensible way of replacing them; this is something you need to be aware of. In a more alarming / extreme scenario you could even be held prisoner by armed captors - so looking at negotiating options and practising these sorts of situations is sensible, and not as over the top as it might first seem.
Then of course you've got the climate to deal with, which can be strenuous and deadly enough in itself if you don't take the right precautions. You're going to be dealing with intense heat and unless you know the specific area you're travelling to very well, you can't rely on stumbling across sources of water like you may do if you were wild camping in "normal" territory. And because of the heat you're going to go through LOTS of water each day.
In summary, I'd say that it can be (just about) bearable, but only if you do a lot of planning, research, and preparation beforehand. Go in a group, make sure you've all done training you deem necessary, tell someone your route and when you aim to be back, run through drills of what to do in emergency situations and contact experts for training on any areas you're not sure of. If you're not prepared to go to those sort of lengths in your preparation then I'd go as far as saying it probably does fall under the category of madness!