http://www.pcworld.com/article/2038798/google-more-than-900-million-android-activations-served.html

This is a really impressive number on its face. The question is how many activations are still being used? Android has been available since 2008, so there are probably a lot of users on the third or even fourth handset since Android’s debut. So this number needs to be kept in perspective.

Regardless, the Android ecosystem is a massive place, and the user base is significant.