Maplex has "Minimum feature size for labeling" option. It's the only way to consider VISIBLE size of features (in page/screen units) when labeling them. Sometimes it's needed to divide features into several classes by their size and label these classes with different settings (font size, placement parameters etc.). For example, lakes. Using "Shape_Area" field in SQL Query is not appropriate, 'cause:
1. When you change projection, areas are also changed. So you need to correct all your SQL queries. 2. When using GCS for layers, Shape_Area is something mysterious and hard to interpret (square degrees). 3. In multi-scale maps you have to use different shape areas for layers with different scale ranges.
It'll be great to implement an option "Maximum feature size for labeling". So the cartographer would have an opportunity to define label classes using minumum and maximum VISIBLE feature sizes (in mm). Scale dependency will be eliminated. Amount of work will be greatly reduced.