The expected behavior is to print out the object and move on: https://github.com/mongodb/mongo/blob/r2.4.8/src/mongo/tools/tool.cpp#L518
However, BSONElement::validate() doesn't validate all types of objects (e.g. arrays):
So if an array contains an invalid object, exception will be thrown when we try to print it out. That exception is unchecked and causes mongodump to abruptly stop.