Making a business out of a game is hard work. It takes great design, unique mechanics, creative marketing and some serious dedication to build a successful game. Turning this successful game into a business requires all of the above, plus a large amount of users that are willing to give you their money. And, if you want to give away access to your game or app for free, as many game makers now do, you will need an even larger number of total users to derive your paid user base from.
The problem with virtual goods is that you need millions of users in order to reach \\$1M in revenue, especially with free-to-paid conversion rates for most social games being in the single digits and average revenue per user (ARPU) often hovering around \\$1. I wrote a in-depth blog post about this (read it here: http://betab.ly/qAe4Vr) and would love some feedback. Thanks!