Membase, The Database Powering Farmville
readwriteweb.com
readwriteweb.com
1. Farmville uses Membase.
2. Membase is related to memcached.
You have to go to Wikipedia (http://en.wikipedia.org/wiki/Membase) to find some relevant info (seemingly picked up from marketing materials, though). Such as: they seem to aim for easy installation and management.
My girlfriend has a ludicrous Farmville addiction, and I don't think she's gone more than a few hours at a time without it messing up and loosing whatever she'd just spent the past twenty minutes doing. If that happened to me more than once, I'm pretty sure I'd stop playing that game.
The admin UI is nice, real time stats are good. It, however is still in the 2nd beta and there are known bugs that need to be fixed to be considered production worthy imo.
If anything, I'm impressed that Membase is standing up to the torturous load of all those strawberry harvests and ponies. :)
We're in the middle of doing some testing with it at Loggly, and we've found them exceedingly responsive to our requests.