They use it as a trivial caching system of pre-aggregated data.
In other words, are there any features specific to MongoDB that they are actually making use of?
e.g. If I run a query for NAME LIKE 'BLAH%' it stores that resultset. If I run NAME LIKE 'BLAP%' it stores that resultset. If someone else comes and runs either of them, only a direct match will pull my prior results.
It's okay, but it's no big win or case study.