Mongoexport exports a zero-valued integer as a zero-valued double.
This means that running through a mongoexport/import cycle changes the type for the field, potentially leading to casting exceptions downstream.

//given: 
db.foo.insert({_id:0, double:0.0})

//mongoexport yields:
{"_id":0.0,"double":0.0}

//should yield:
{"_id":0  ,"double":0.0}