Here is a world map showing the percentage of people using the Internet per country: http://upload.wikimedia.org/wikipedia/commons/a/af/Internet_Penetration.png
Some countries cannot afford to install/maintain the infrastructures needed to run the internet have, other ( like China ) restrict Internet access as a form of censorship
Wow, africa the bleak continent. I guess a good place for holidays. When your online on holidays you end up checking your mails, twitter, facebook all the time. And find yourself spending more time "at home" than in the country you are actually in. I'd love to spend my next holidays in a country with NO internet. :)