Run:

$ python simple-setup.py --chunksize=1

In the shell:

> for(i=0;i<10000000;i++) {db.foo.insert(

{x:1,y:i,date:new Date(), str:"all the talk on the market"}

); }
> db.foo.count()
10000000

Export this collection:

$ mongoexport -d test -c foo -o foo.json
connected to: 127.0.0.1
exported 2610450 records