I've got 2 teenagers (who, BTW, aren't very technologically savvy) and
they find ways around the restrictions fairly easily (it's all that
darned IM'ing
By restricting things, you send the message to your kids that there's
something bad out there that they shouldn't see. Being normal kids,
they want to see what it is. This serves 2 (or more) purposes. It
helps to instill values in kids based on the parent's values and it
encourages creativity to see what they're not supposed to see, and it
encourages independence when they've got to decide if they should
believe you (about what you've forbidden) or not, and it encourages
caution when they see that it may cause problems for them (either by the
forbidden thing itself - or by the fact that Mom & Dad may catch them).
I was a Sergean Major in the US Army before I retired - and I was very
good at forbidding things! I've found that, with my kids, that things
just don't work that nice in real life. I set things up to protect the
kids, but don't go off the deep end when they go out and try to do
things on their own.
Finally, if you catch them doing things, you've got 2 options
1) Read them the riot act and make them even more cautious when trying
to get away with things (so that you won't catch them).
2) Play your cards close to your chest. You know where they are and
what they're doing. If you spill the beans about that they'll do
something else - so why not just be a "stealth supervisor"?