BTW, I think you will also find that different peoples fermentation techniques will either exacerbate or reduce the exothermic action. The amount of yeast you pitch, how healthy that pitch is and how warm you pitch all make a difference. I have noticed when I pitch warmer the fermentation seems to go closer to the 6-8 degree mark. When I pitch cooler sometimes it only goes 2-4 degrees warmer. My lagers don't seem to be much more than 4 degrees over, ever. I pitch them at ~44 usually.
However, seeing how important fermentation control is it also surprised me how lacking the available literature is on the subject as well. Doesn't make sense to me that fermentation is easily the most important part of the brewing process - regardless how well you get you water chemistry, how well designed your recipe is, if your fermentation techniques are flawed your beer probably will be too. And yet, Palmer goes on and on and on about water Chemistry yet suggests to put your ale in an ambient room of 72 degrees.