This was brought up in a big way in the recent firestorm around Mongo, but the lack of joins precludes it from any use as a relational database (which is fine,

This was brought up in a big way in the recent firestorm around Mongo, but the lack of joins precludes it from any use as a relational database (which is fine, since it's not intended as one). However, I've never been able to use Mongo as a large-scale store as a result. It seems like the addition of joins lends some relational capabilities which in my eyes is very impressive. I'll be watching the advance of this one with interest.