It’s never ceased to amaze me how many people honestly believe that making something off-limits will protect others. It rarely works that way, mainly because forbidding something just triggers the innate curiosity we’re all born with.
Rather than block access to something you perceive as dangerous, teach the people you’re trying to block out. Teach them what the blocked item is, and then explain why you feel they shouldn’t go near it. It’s far easier to get a toddler to not touch a hot stove if you help them understand why than to just tell them not to do it.
Adults are much the same way. If you tell someone to not do something, and the best reason you can come up with is some variation on either, “Just don’t do it,” or, “Trust me,” you can rest assured the other person will do it. You haven’t given them an actual reason to listen to your advice. School districts are learning this the hard way as they’re slowly coming to realize their students will be far safer with lessons on how to live online safely than if they block MySpace and Facebook from school networks.
People, regardless of their age, respond best to reason. Even those crazy, rebellious teenagers are more likely to actually listen if you can give them actual reasons. If you forbid, regardless of the age, you’ll lost your audience.