My husband was just throwing some oil-coated bakers in the oven, and I asked him if he'd poked them. He hadn't yet, and then did so, then asked me, "Isn't that an old wives tale? Isn't only for microwaves or..."
The first time I learned about poking holes in potatoes before baking was long before I'd ever heard of a microwave, but that doesn't really mean anything.
I tried a search of the web in general and a search of Chowhounds, and couldn't find anything definitive.
In a microwave, the exploding potato story sort of makes sense. But in a conventional oven? Does anyone know?
I do it because that's what my Mom taught me. (Keep in mind, though, like the "cutting the ends of the ham" story, I thought you were supposed to cut the ends off the potatoes before baking because my Mom always did...and years later realized it was because she always bought #2 potatoes, and the ends were...questionable. I learned the poking thing from the same person.)
(Feel free to steer me toward an appropriate Chowhounds post if it exists. I couldn't find it on search.)