It's not a matter of whether the internet is global, its who your audience is... if you audience is primarily in developed nations, then the rest of the world isn't much of an issue.
If you're running a purely domestic web store, maybe, but people in developing nations are not that different from people in developed nations, they can be just as interested in a a wide variety of topics, that's what makes the internet so appealing and wonderful.
Sure, we're humans and all, but jmcdiesel isn't saying that people in the developing world aren't interested in similar things, just that many businesses do have audiences which are limited to certain countries.
Much of the internet is a business, not a passion project. There are plenty of businesses that are completely OK with being inaccessible to users on 2g/3g in the developing world.
Even if you're running an international web store, shipping to developing countries plus the increased rate of fraud and different payment technologies generally mean that you're not keen to expand to those places anytime soon.
