My parents never did it, and I doubt I would, had I children. It seems old-fashioned to me. I think it could be done abusively, but I'm not sure it's inherently abusive.

I knew one family that I knew did it in some circumstance; they put a drop of liquid (dish?) soap on their daughter's tongue. I kind of think it was for being disrespectful, rather than swearing, but it's been a long time since they mentioned it. (It came up in conversation once, more than 15 years ago. I was somewhat surprised to hear people still did that.)