Facebook is booming in Turkey and Indonesia. YouTube’s audience has nearly doubled in India and Brazil.

That may seem like good news. But it is also a major reason these and other Web companies with big global audiences and renowned brands struggle to turn even a tiny profit.

Call it the International Paradox.

Web companies that rely on advertising are enjoying some of their most vibrant growth in developing countries. But those are also the same places where it can be the most expensive to operate, since Web companies often need more servers to make content available to parts of the world with limited bandwidth. And in those countries, online display advertising is least likely to translate into results.

This intractable contradiction has become a serious drag on the bottom lines of photo-sharing sites, social networks and video distributors like YouTube. It is also threatening the fervent idealism of Internet entrepreneurs, who hoped to unite the world in a single online village but are increasingly finding that the economics of that vision just do not work.