Default Setting for Text Boxes - Do Not Resize

I'm going to take a stab in the dark here, but I'm guessing that the reason for the default of Autofit is because it's a holdover when importing from PPT, where the default setting is to Autofit, and along with the slides themselves, SL imports the master slide styles from PPT. It doesn't automatically use whatever master slide style that you've set up in SL. So if your text boxes in PPT are Autofit, they'll come over as Autofit, and if not, they'll be set to whatever the PPT master slide text box setting is. 

I admit it's a pain in the butt, too, to have to touch every text box to change the setting to Do Not Autofit." Unfortunately, SL doesn't have the same kind of setup feature as Captivate, which allows you to apply a setting to all objects of the same type, which is really what we're asking for in SL. And this can be set up in advance, through the Captivate Preferences.

Oh, how most of us are dreaming of the day when the best and most powerful parts of Captivate and the best and most powerful parts of SL are combined into a single program...sigh...