What they may be referring to is that most countries these days require you to separate your laptop from your carry-on - that is, to take it out of the bag. Evidently this helps them check it more thoroughly than having it inside lots of other stuff - quite often other electronics. I've had this happen on every flight for the last few years, and it's common practice.
However, in every country, theft can happen at this point. I always wait at the front of the scanning machine until all my bags have moved 'safely' into the scanner and out of the reach of any hands.
At that point, move through the metal detector, and around to the other end of the scanner. Watch for your bags, and collect them quickly. In the event they question you about a bag, or want to check it, ask them to wait until you've got all your bags together, and then walk with them to the manual inspection area. You're entitled to not be separated from your stuff, and if they need to move it elsewhere for another check, be firm but insistent that you go with it. This is very unlikely, and odds are that you'll just pick up your bag and that'll be it, but by just being safe and sure, it eliminates a lot of the small risk.
Oh, since you asked about other electronics - I've twice had people ask me to turn my laptop and my digital SLR camera on to prove it works. I don't know if this is to prove it's not just a container or something weird, but that's all they asked. Glad the battery was charged :)
(And yes, this includes travel to South Africa - although I was last there in 2005 and 2008, but certainly had electronics with me!)