From the three engines of growth[1]: - virality index - retention rate - customer lifetime value / customer aquisition cost Having more than one is hard, so

From the three engines of growth[1]: - virality index - retention rate - customer lifetime value / customer aquisition cost Having more than one is hard, so optmizing for one is much simpler (don't kid yourself, it is hard on any of them, and not all business can pick all of them). [1] http://www.deviantbits.com/blog/engines-of-growth.html http://www.deviantbits.com/blog/engines-of-growth.html