Leaving modifiers unapplied becomes undesirable when the object's geometry gets too complex. Simply performing Boolean operations on cubes together may not cause a crash, but adding Boolean operations to multiresolutioned objects and moving them around or changing the order of their modifiers has been known to slow down or even crash even the heartiest of systems.
Try to see how quickly Blender will slow down by making several cubes, adding multiresolution modifiers to increase their polygon count and Boolean them together all without pressing the Apply button. Add more and more multiresolution cubes and move them around to see when performance becomes choppy. It may be surprising how little time it takes.
With the measurements of an SD card available, any object can be turned into an SD card holder. Why not make an SD holder key chain or an SD holder that clips to a breast pocket? Add an SD holder to a mini mug or vase to turn decorative items into something functional. Measure...
