If you know me, you know I am aggressively addicted to Sporcle. One of the quizzes I've spent the most time on is probably the capitals of the world, in an effort to learn all of them myself. Eventually I got there (yea, I'm looking at you Melekeok Palau, Naypyidaw Myanmar, and Bandar Seri Begawan Brunei), but in the process I felt like making a map of the most-commonly guessed capitals.
Obviously, Sporcle is an American- and English-biased website so some of this data is probably skewed. But as you see, most people tend to know America, Russia, Japan, and western Europe; and, as expected, know very little about Africa.