[ineedasername]

nothing will ever defeat a determined X from doing Y

I hate when this line of thinking is marched out in defense of an all/nothing approach-- The idea that you don't have a perfect solution, so you shouldn't even bother trying to implement something less than perfect.

There's no reason not to do something that discourages bad activity just because it won't be perfect. With kids especially, they may find a way around a restriction, but that doesn't mean they will always avoid detection (though sometimes they will) And in those cases it also provides a good parenting opportunity to teach lessons on consequences for the decisions made.

At a minimum, you can't simply fail to set reasonable limits just because they may not be followed. An understanding of such limits, if not a full appreciation of them, it pretty critical. And a total lock-down approach of "no X ever ever" is fairly likely to catalyze into a backlash much worse than trying to work with your kids on appropriate limits and then monitory things as they go.