I'd like to think it was rare to spank a baby, but I have seen my own cousins do it to their dc
...it is not at all uncommon in rural Louisiana, where I have family. I would be shocked, however, to see anyone I know here in California spank their baby. Different culture.
I never heard of blanket-training, though, until I heard about the Duggar family! Sadly, through my kindergarten experience, I *did* know about paddles. I got paddled once in K, for leaving the single-file line down to the playground to look at something, and it was such a humiliating experience that it has overshadowed anything positive I might have otherwise remembered from Kindergarten. It was so nice the next year in 1st grade when we moved back to CA and I didn't have to fear my teacher anymore.
(Sorry to go a bit OT! But thinking about the paddle brought back awful memories.)