I did some usability testing on the drawing layer that was added to Microsoft Word back in Word 6 -- so around 1992. One study specifically looked at the UI for resizing and moving objects. There were several interesting findings. The most important was that the conventions commonly used (grab objects by solid edges to move them, grab by "grow handles" to resize them) is not very intuitive. When naive users want to move objects, the grow handles seem like plausible candidates to many. And as you noted it often seems reasonable to click and drag in the middle of any region to move an object, though this isn't feasible with some objects. A second finding is that discovery of the "correct" methods is a surprisingly steep curve. Inadvertently resizing objects is frustrating and does not lead easily to deducing better interaction alternatives. It's a surprisingly hard UI problem calling for creative alternatives. On that point the third interesting finding is that creative alternatives may not be well received by design or development teams. At the time I did the testing, we compared results with the UI from Microsoft Publisher. In the Publisher UI the mouse cursor switched to a little moving van when the mouse moved over anything that could be used for dragging. This gave immediate feedback that the grow handles were not intended as a tool for moving objects. Ultimately the Word team decided the moving van didn't look professional enough, despite strong usability results. As an aside, some members of the Excel team resisted the idea of changing the arrow cursor for any reason, but lost to consistency within the Office apps. A fourth finding was that the strong difficulty with discoverability of the drag vs. resize UI that has been implemented for so long is not a function of age, education, or intelligence, though when educated geeks see such dramatic results in the usability lab they may be tempted to jump to these conclusions.
This study is obviously not comprehensive, especially regarding current UIs. I just want to encourage you to consider it an area for potential innovation, one where further study with a sizeable pool of novice users would be worthwhile.
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