It’s one of the smallest nations in Africa, roughly the size of Hawaii with a population of half a million. Yet the former Spanish colony of Equatorial Guinea tops the list of iPhone-using countries compiled by Net Applications, which issued a report on Friday that ranks them by the relative frequency with which the Web was accessed in January via an Apple (AAPL) iPhone.

“We’ve heard the rumors that many iPhones are being used outside the officially sanctioned countries,” writes the net service company in iPhones Without Border. “So, we decided to check it out and surprise, surprise, it’s true. The iPhone has a presence in almost every country on earth.”

The full list can be seen at NetApplications.com. I’ve pasted as much of it as I could fit in a screen-grab below the fold.

Given that Apple has only sanctioned iPhone use in four countries — the U.S., the U.K., Germany and France — it’s amazing how widely it is now being used. If you were wondering where those 1 million unlocked iPhones went, this may be the answer.

In fact, there were only five countries in the survey where the iPhone did not show up — South Korea, Lithuania, Taiwan, Malta and Iran — perhaps in some cases because GSM and EDGE aren’t supported there.

It’s also surprising, at least at first glance, how many third world countries turn up near the top of this list. Two out of every 1,000 Americans now surf the Web using an iPhone, according to Net Applications, but in the Ivory Coast that number is nearly five per thousand. In Equatorial Guinea, it’s better than two per hundred. [UPDATE: It has jumped overnight to more than one in ten in Equatorial Guinea, according to the weekly stats.]

Or maybe it’s not so surprising, given the explosion of cell phone use in Africa over the past five years (see, for example, here). In countries where wi-fi and Ethernet connections are rare, a $400 iPhone may be a relatively cheap and dependable way to reach the Internet.

And it’s really not so surprising to find Equatorial Guinea in the No. 1 spot. The country’s economy has boomed since the discovery of offshore oil reserves in 1996. According to the CIA Factbook, Equatorial Guinea now has the fourth highest per capita income in the world, after Luxembourg, Bermuda and Jersey.

The news was almost lost yesterday in the Microhoo hoopla: even as Microsoft (MSFT) was trying to buy its way into some kind of parity with Google (GOOG) by gobbling up Yahoo (YHOO), a new survey showed that Apple (AAPL) had taken another little bite out of Redmond’s core business.

According to the latest market share data from Net Applications, Mac OS X’s slice of the computer operating system market grew 3.56% in January while Microsoft Windows’ dropped .36%.

As Net Applications measures it (more on its methodology below), the Mac’s market share stands at a record 7.57%, up 21.7% from Jan. 2007.

“Apple’s market share gains in December for the Mac and iPhone are impressive,” the report concludes. “However, for the last days of December, the numbers are nothing short of spectacular.”

The really good news for Apple, according to Net Applications, came in the last two days of the month, when Mac OS X hit 8.01%.

Windows is still dominates the desktop, of course, with a 91.46% share, but that’s down from 93.33% a year earlier.

Net Applications’ monthly surveys sample data from visitors to some 40,000 websites operated by the firm’s clients. As such, the findings are a snapshot of installed base rather than a month-to-month measure of computer systems sold. The January results are summarized in the table below. The full report can be viewed here.