I do not mean to comment out of point, however, I just want to point out that to me, there seems to be 'something' about branding a part of the world 1st World and another 3rd World.
"Developed countries" and "Developing countries" seem better terms to describe the infrastructural distinctions.
Well, it originally came out of the Cold War, so I guess there is definitely something a little weird about it. Personally I don't really care for "developed" either though; it implies to me that those countries have achieved some peak of civilisation and don't need to change any more, which plainly isn't the case.
It's probably more pejorative than "third world", but "rich" and "poor" are probably clearer descriptions for a discussion of cellphone usage patterns than most of these euphemisms. That'd upset people even more, of course :)
You could perhaps look at "developing" in terms of economic growth - most "developed" countries have relatively low growth as their economies are mature.
That's not to say that all countries with low growth have mature economies of course, just that "developed" countries are at the economic forefront, and that "developing" countries need to make an effort to catch up or be forever "developing".
In terms that most people could understand "rich" and "poor" may be more accurate, but in terms of cell phone usage there are quite a few African countries that have widespread mobile phone networks, but few wired telephones.
You could perhaps come to think that the above sort of labels are very generic, but I do think that for a start that talk of a third world/first world split is not useful when the second world - communist russia and its ilk - doesn't exist anymore.
"Developed countries" and "Developing countries" seem better terms to describe the infrastructural distinctions.