chubby - Like others have said, the switch is much more likely to get flipped down, than up. Considering that you SHOULD be landing on your wheels, the impact will push the switch down. Now if you're landing upside more often than right-side up, then it's a different story...haha.
You shouldn't really have to worry about anything hitting the switch and pushing it up. It's tucked away pretty well.
Also, for extra insurance, you can mount a piece of lexan to one of the switch mount screws, cut into shape that when swung into place, will hold the switch in the on-position, like this (it keeps changing the spacing, so it might look weird):
___| |<-- the switch will go right here, which will hold it into place.
|_| <-- drill a small hole here to mount it to one of the screws.
Of course, you'll have to swing it out of the way to turn the switch off, but it's much more convenient than running no switch and having to plug and un-plug your receiver pack all the time.
Aaron Waldron - LiveRC