If you don't trust your children to understand your lessons about being careful online, do you install cameras on their way to school as well? Do you read their text messages and diaries? Is this seriously acceptable/normal over there or is this explicitly targeted at Facebook/social media sites?
For me this seems like an easy way out. If you are suspicious that your own kid does something you don't like (Yeah.. And you never did that in the good old times..), let's just snoop out their communication on Facebook.
And - as we all know - the things you say or write as a kid are like totally acceptable all the time. You'd never talk bad about things your parents like and you'd always like your parents to check out the people you've got a crush on..
Edit:
You suggest a kid can use a computer at another kids house (to do stuff on the 'net that has to be controlled) but trust your kid to not abuse the distance to your home in other ways? "Yeah, she's over at a friend's. Hope they're not on Facebook again."?
More likely, the purpose is to grandstand and give technophobic/worried parents the impression something is being done on their behalf, in the hope that they'll vote for the politicians responsible in future. Whether the law works is irrelevant.
If I were a parent installing monitoring software, I think I'd tell my kids exactly what the software monitors, show them the logs, and teach them a way to get around it that logs access times but not content. I would say, "If you need to hide something from me, that's cool, but I'm going to know that you hid something and I'm going to ask about it, so keep that in mind." The purpose of the monitoring software would be to provide an opportunity to analyze the potential consequences of my kids' online activities.
Of course, imagining and doing are very different things, so ask me again in n years after I've actually started a family and see if I actually followed my own advice ;).
Bottom line, monitoring your child is part of being a parent and there are already tools in place to help with this. As the saying goes Trust but verify.