I'd imagine doing so would drop/cancel whatever objects your dragging/dropping with your mouse. I often drag an object, hit the top right corner of my screen (hot spot) thereby activating *All Windows* Expose which gives me direct access to any open document, I hover over the desired window for a split second and it goes to this window where I can drop my object that ive held down on left click the entire time. This whole process takes *zero* clicks to do, just a simple swipe to activate Expose from the hot corner.
This whole debacle could be *easily* solved if Apple pulled its head out of its a$$ and eased up on not giving users options. By this I mean, it'd be a simple checkmark field in System Preferences to let the user customize Mission Control to their liking, or AT LEAST give the option to turn off grouping.