A few weeks back, Ryan Kennedy of Yammer gave a talk about Berkeley DB Java Edition. You can find it posted here on Alex Popescu's Blog, or go directly to the video post itself. It was full of useful nuggets of information, such as why they chose to use BDB JE, performance, and some tips & tricks at the end. At over 40 minutes, the video is quite long. Ryan is an entertaining speaker, so I suggest you watch all of it. But if you only have time for the highlights, here are some times you can sync to:

 06:18 hear the Berkeley DB JE features that caused Yammer select it, including:

• replication
• auto leader election, failover
• configurable durability and consistency guarantees
  

23:10 System performance characteristics

35:08 Check out the tips and tricks for using Berkeley DB JE

I know the Berkeley DB development team is very pleased that BDB JE is working out well for Yammer. We definitely encourage others out there to take note of this success, especially if your requirements are similar to Yammer's (which Ryan outlines at the beginning of his talk)