Ehhh, I have to admit when I made the purchase of DJW.net from BuyDomains, I noticed DJW.asia for sale as well. I asked the price and it was $400. I attempted to talk them down, but it was a private seller. I was about to make the purchase, for my .asia travels (I plan to visit every Asia country and have been to quite a few already) and blog about site seeing spots and "sight seeing" spots. However, $400 was too much to purchase my initials in .asia and decided to just do it on DJW.net as a noindex sub-blog. That was the slightest value that I have seen in .asia.
For .africa, DJW will not be visiting unless one day I want to go on a safari or something. But who needs that when you can see wild monkeys run around in the streets in Asia?
As far as having .Africa, only 10% natively speak English or use it as a secondary language. It'll be hard to target the 3000+ languages used in Africa with the 1.1 billion people. (And of them, who has internet access?)
Whereas out of 3.9 billion people in Asia, 1.4 billion speak English fluently or as a second language (35%) and are "connected".
Though, where Asia failed I believe is that Asian countries have strong pride. Natively, they will speak their official language and thus most likely use their own ccTLD's instead of uniting as one.
.Africa will fail with both language barrier, the constant battles between countries and lack of connectivity though.
If you do go out and register .Africa go for all languages of one product (games.africa, Afrikaans: speletjies.africa) and you may have a higher chance of succeeding, once they have computers ... that support Flash ... and internet.
I foresee .africa falling on its face quicker than .asia though.