Beyond technical hurdles such as whether to tax mainland investors as domestic enterprises or as foreign ones, the larger issue is concern about the "shallowness" of Taiwan's economy. Specifically, the fear is that mainland capital might become annoyed during the course of a cross-strait standoff and flood Taiwan with capital.
除了有課稅方式到底是准用「國內企業」還是「外資」等技術性障礙外，最主要當然還是顧慮到台灣本身的「淺碟經濟」性質，怕兩岸對立中，陸資一個不爽，就從活水變身洪水猛獸，反噬台灣。