Yeah, I have a couple of Picos and I'm inclined to agree. I don't see how a significant amount of juice gets into the battery compartment because of a little topper leakage. I'm not implying that you're being untruthful- I would guess that if you're finding a lot of juice in there it's getting there through a different mechanism (so I suppose I am implying that your wife might be a bit messier with juice than either of you realize. Please don't track me down and shoot me for insulting her honor.)
Meh..... not insulted. I wonder now, could it be that it somehow gets in there through 510 pin connector? If liquid drips to the bottom of the device, perhaps it is not through the cap, but rather through the pin and into the battery compartment?