can you overinsulate?

I was wondering about this in a recent post: can you overinsulate? Apparently I'm not the only one. Reduced to first principles, heat flows as heat flows, so it seems that what's good for keeping heat in is also good for keeping heat out. My bride (the engineer) and I have chatted about this from time to time (it's that kind of exciting relationship...), and it's mentioned in this article and debate over at Green Advisor: perhaps it's due to temperature difference. The temperature difference in Minnesota is larger than the temperature difference in Texas. Up north, you may be fighting to keep the T at 75 inside while it's 10 below zero outside (a difference of 85 degrees!). Down south, you may be fighting to keep the T at 75 inside while it's 105 outside (like today...), a difference of "only" 30 degrees. Perhaps this is why energy recovery ventilators work better (greater efficiency) in heating climates than in cooling climates?

Furthermore, there are a lot of heat sources in a house: the stove, the computer, the TV, the cat, you. In a heating climate, these heat sources help you. In a cooling climate, they hurt. And there's the humidity issue. I like the comment in the article about someone sometime designing appliances for a hot climate. I'm still losing sleep over how a clothes dryer takes indoor (cool!) air, warms it up, and then disposes it the outdoors. Not cool! (so to speak...). Certainly not efficient.