Share 'Instagram's impressive achievement - a million users!'

Instagram is probably one of the first apps that gained over 1 million users in such a short period of time – three months. Even twitter, the so powerful platform, needed about two years to achieve this number. Right after app’s launching it was clear enough it would show great results considering the service got the first 100.000 users in less than a week.  What’s the secret? A key to such great…