(Click to enlarge or see Google Insight link)
I used insights to show the results for the terms 'porn' or 'sex'. Also notice that the top 4 countries with the highest search volume for these terms are all South Asian -- Pakistan, Bangladesh, Sri Lanka and India. A SAARC orgy anyone?
In any case, I can think of two possible explanations for the results.
First, in lower-income countries, the utility of non-porn related internet activities (searches in this case) are low. There's no real thriving e-commerce industry, so searching for soap, books or mini-skirts wouldn't yield much. Nor do people search for things like local news on general search engines like Google, because of all the noise created by 'western content'. After all according to Alexa 9 of the the 100 most visited websites in Sri Lanka are porn-related.
But there are few kinks with this hypothesis. If this were true then most lower-income countries would have higher proportion of horny-searches. This isn't exactly the case. Nigeria for example has a much lower per-capita income level than Pakistan and it produces less horny searches than the U.S.
The second explanation, (which I think is more to the point) is this: All people are horny. But countries of who's cultures promote a hush-hush attitude towards sex, find other means to satisfy their horniness, such as watching Internet porn. Notice that middle-eastern countries such as Egypt, Yemen immediately follows their South Asian counterparts in the horny search index.
Conclusion: we are just bloody sexually-oppressed and bored on the Internet. But you didn't need me to tell you that. Bugger, what a waste time..
Notes : 1) Google Insights normalizes all data. Biases resulting from higher-search volumes of certain countries are removed. 2) Horny-country inspiration from IndiaUncut.