A properly working mass airflow sensor is essential to your engine running smoothly.
When a mass airflow sensor goes bad the engine will run rich at idle or lean when under a load, the engine will also idle rough and your gas mileage will suffer.
If the fuel is not burnt properly then the engine could potentially be damaged and you could become stranded somewhere should the engine decide to shut off due to the bad mass airflow sensor and not start again.
A bad mass airflow sensor can cause an engine to be hard to start or not start at all.
You could drive with a bad mass airflow sensor but I would recommend getting it replaced before more problems occur.