I know of a girl who used to knock out her son for 18 hours at a time if he ever "annoyed" her. Or if she wanted to go out and he wouldnt go to bed before she wanted to leave she would do it. So then he would be still knocked out when she got home

And it was the FIRST thing she said to me when she found out i was pregnant. I then cut her out of my life and still refuse to talk to her.

I agree if used correctly and as the VERY last resort then there is no problem that i can see. I also agree with making sure you have a lot of activities for your DS to ensure hes not unsettled or gets bored.