OK, it's time for somebody to do a scientific study on the effects of wind on a modern tent :-). And, provide us with a definition of breeze vs. wind.
I haven't staked a tent down in more than thirty years (The old canvas ones we used needed to be staked down, or they wouldn't stand up.), and during the summer, when I leave the "fly" home, I rarely do more than throw my pack inside. I've never lost a tent.
The suggestions to place a rock through a sting loop, or over a stake placed through the loop, should hold the tent in place in everything short of 50+ mph winds. DON'T PUT ROCKS INSIDE! This has the tendency to abrade the material, a you'll likely end up with holes in you tent.
Of course, none of this applies if you're using a $25 Kmart special. If you are, you'll have to spend the night with you feet up against the wall (like I did one late-winter climb) all night long.