Border guards in the Schengen area in Western Europe screen foreign travelers in a database called SIS. Someone in violation of Schengen duration stays might (I could be wrong) have their passport flagged in the SIS in the form of an alert or notification.
Do Schengen member countries share SIS data or alerts with other countries (e.g. USA, Australia, etc)? For example, if you try to enter the USA, will an American border guard see that you have outstanding passport violations in Europe?