By the end of December, according to Piper Jaffray’s Gene Munster, Apple (AAPL) will have sold nearly 78 million iPhones and iPod touches worldwide.

So where, exactly, are those devices?

A report issued Friday by AdMob, the world’s leading supplier of mobile ads, tries to map the location of Apple’s handsets country by country based on the number of users who requested at least one of its ads in November — a number that increased 150% in 2009.

Among the highlights of its findings:

• In November, 50% of unique Apple visitors were located in the United States. The next four biggest markets were the U.K., France, Canada and Germany.
• In total, 23 countries had more than 100,000 unique Apple visitors.
• 50% of unique Apple users were located outside of the US, up from 39% in January 2009.
• The iPhone accounted for 71% and the iPod touch 29% of the total unique Apple users in November. In raw numbers: 18.0 million iPhones; 7.3 million iPod touches; 25.2 million total.
• The fastest growing countries between January 2009 and November 2009 were Japan, France, Australia and China. See the bar graph below.

AdMob describes itself as the world’s largest mobile advertising platform, serving banner and text link ads on 15,000 mobile Web sites and iPhone and Android applications. Its reports are based on  handset and operator data on nearly 138 billion impressions. They do not, however, measure mobile markets in the traditional sense of number of handsets sold. And they have a bias toward devices like the iPhone and Droid that visit ad-supported websites and also run ad-supported apps.

You can download their November report as a pdf from metrics.admob.com.

[Follow Philip Elmer-DeWitt on Twitter @philiped]