BitKRW definitely belongs on our list. For its blend of a large economy, tech-savvy population, nearly universal High Speed Internet, highly educated and banked population, and a lot of Koreans living abroad, South Korea is a rare market.
South Korea (Republic of Korea) has one of the largest economies in the world. If you subtract some countries that are basically just selling off their resources, it easily makes the Top 10 (and this is a country that basically has very few natural resources, so that's how industrious they are). It also ranks VERY high in surveys of the most high tech countries in the world, often placing between #2 and #4 on that list. There may well be more Koreans connected by High Speed Internet than any other group in the world. With all the Korean people living in other countries, such as the United States, Japan, and Canada, money transfers should be a big business. This is a highly educated, comparatively wealthy, highly tech-savvy population.
Bonus: there are a good number of Filipino workers in Korea. They get paid in KRW. When Underwood gets his remittance thing going...
Source: Lived there.