It happens to me too. I originally thought it was due to misaligned wheels, but there's no problems there. Alignment is perfect. It happens to me mostly over bridges and high altitudes, and sometimes, though rarely, even driving 30mph with gusts over 50mph. If you all remember how the midwest was hit this last summer with that storm, that's where the last comment comes from.
I've done a lot of searching on this, so here's a few tips to take into consideration:
After polling 15 people who have driven without and with their front strut tower brace, they claim that it helps maneuverability under heavy winds. It doesn't keep them from being blown but there's better control mid-sway.
Same as above, I asked 8 people who have front sway bars and they say the same.
Same with rear strut and sway bars. (3 polled).
If you ask me, a more sturdy barn would increase the chances of being blown around; though this is one of the main reasons I got myself a rear sway bar. I want to see for myself what handling becomes with it.