[@_ck_ Participant 16 years, 3 months ago]

bbPress is currently installed on at least 5,000 sites.

Here is a breakdown of bbPress forums by total posts:

Posts 		Count

0 - 99		3,000+

100 - 999		 640

1,000 - 4,999	 180

5,000 - 9,999	  52

10,000 - 49,999	  44

50,000 - 99,999	  12

100,000 - 499,999	   7

500,000 - 999,999	   2

By my calculations, a bbPress forum will break a million posts by the end of this year!