30/10/10 rule
July 30 2011, 12:59 PM
30% of the registered users or number of downloads (if its a mobile app) will use the service each month
10% of the registered users or number of downloads (if its a mobile app) will use the service each day
the max number of concurrent users of a real-time service will be 10% of the number of daily users
We see these ratios across social web apps, social mobile apps, games, music services, and many other consumer web and mobile services.