Metrics on app downloads vs usage

Fred Wilson has an interesting post on metrics they see across tech startups.

We see a lot of metrics on web and mobile apps. [...] 

One thing that never ceases to amaze me is how similar some of the metrics are from service to service and company to company. I like to call these the web/mobile laws of physics. One fairly common "law of web/mobile physics" is the ratio of registered users/downloads to monthly actives, daily actives, and max concurrent users (for services that have a real time component to them). 

I call this ratio 30/10/10 and so many services that we see exhibit it within a few percentage points here and there. Here's how it works:

• 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.