in my opinion, gmail became big when it was a kind of status symbol to have a gmail address. I doubt that ever reached asia. but at one point, there were people with gmail addresses, and people with yahoo and hotmail addresses. and if you had a gmail address and you met another person with a gmail address, you knew that person was "in the know." At that point in time, switching email addresses was seamless -- you'd just switch email addresses. nowadays, you're using email for important things. even just a little bit of inertia would probably keep many people from switching.