OK, so baking soda didn't really eat my face. It just left spots red, flaky, and mildly stinging after several months of use.
I did some research--yeah, well, I Googled--and learned that baking soda throws off your face's pH balance. See, your face's skin is slightly acidic, with a pH balance somewhere between 4.6 and 5.5. This acidity helps ward off infection and damage. But baking soda? That's an alkaline. The pH level of baking soda is at least 8.0 (some sources list it as high as 10.0), and it strips away the mantle protecting your skin.
In other words: Baking soda might be effective at keeping your acne under control, but you'll be trading it in for new and potentially much more serious problems.
Darn it. Apart from the whole damaging-the-skin part, I was pleased with baking soda. It was very effective for controlling my acne and zapping the occasional whitehead. I'll keep using it for spot treatment, perhaps, but no more facial masks.
I hear you can counterbalance the effect by using watered down apple cider vinegar as a toner, but I'm not eager to try it.