Yes, sinkholes are becoming more common. While sinkholes have certainly always existed, mining and draining underwater lakes makes them far more common than they would occur naturally. This is unfortunate, as it presents a danger and hazard for any living in the areas that these artificial sinkholes may end up forming.
Sinkholes are a common result of erosion and the collapse of the surface layer. Any natural happening that would cause this type of activity is not becoming more common. What is becoming more common is the development of areas where this type of activity has went unnoticed in the past.