I don't know the number, but there is an amount of spankos who weren't spanked as children, who come to spanking because they felt like they missed out by not getting spanked. That may indicate a flaw on psychological thought behind corporal punishment as well, just seeing as how seemingly "common" it appears to be here.
Regarding laws, just because something is illegal, doesn't mean it isn't being done. That's all I'm going to say on that one.
Younger generations will still find references to spanking somewhere, and it might pique their interest. Granted, they might know the other terms that were used to reference spanking. For example, I remember in middle school a teacher pointing out the line "and the seat of his pants were dusted" to mean the character in the poem got spanked.
There's a clothing line called "Spanx", that alone, is probably enough to get people searching.