e-diplomacy is the talk of foreign ministries the world over, as foreign affairs is increasingly conducted in 140 characters or less.

In fact, it isn't far from the total of all the students who have ever been there since the 19th Century.

Daphne Koller, co-founder of Coursera, says the expansion of online courses will raise difficult questions about what mainstream universities offer for such high fees.

if the content of university courses becomes freely available, what is it that students are paying for? Is it the interactions with staff? Or is it the time with other students? Is it something to put on a CV? "This is causing universities to rethink their value to students," says Professor Koller, who is from Stanford University's computer science department. The most prestigious universities are always going to have enough demand for places - but the emergence of high-quality online courses could be tougher for middle-ranking institutions. Why would you pay high fees to sit through a mediocre lecture, when you could go online and watch world experts at another university, even if it's in another country? "The universities in the middle will really have to think about their proposition," she says.

Other trending nations include Indonesia, which has 29.4 million profiles and the most active Twitter city, Jakarta

Research by Dr. BJ Fogg at Stanford’s Persuasive Technology Lab indicates that reducing the effort involved in completing an action increases the likelihood of that behavior. Simplifying the experience is key.

Among the most powerful methods for increasing the probability of a behavior is providing rewards on a variable ratio. In other words, when the behavior produces varying amounts of benefit, the user increases the action. Variable rewards can be found at the core of all sorts of addictive behaviors.

Many companies are afraid to ask the user to do work. They follow the mantra that good design should get out of the user’s way, but they often take it too far and forget that asking the user to do some work can be a very good thing. In fact, exerting effort makes people value outcomes more highly