I thought that e-commerce was one of the things MongoDB said it would not be good for http://www.mongodb.org/display/DOCS/Use+Cases#UseCases-Whens...
I love MongoDB and I use it on many of the projects I work on, but I'd want something transactional and ACID compliant when dealing with money and purchase tracking. How are you mitigating the risks of data integrity compromise when using Mongo?
There are ways to perform document-level transactions using optimistic or pessimistic locking, in our experience so far this has been sufficient for purchase tracking. I imagine our perspective will mature as we get the system into higher load scenarios.
One of the reasons we decided to delay code release is that we need more time/resources to get it ready for the different ways developers will try to use it early on.
