The mantra we use with our kids is "We will try and respect your privacy but we aren't bound by it." As I often tell my son, "It's your room but it's my house."
And we make it extra clear that the moment they go online, they have no expectation of privacy. Better they learn that someone's snooping now than be surprised when it's Google/Facebook/NSA.
I think most children find it significantly more invasive for their parents to be snooping through their messages, than to have that information being collected in some government database.
And we make it extra clear that the moment they go online, they have no expectation of privacy. Better they learn that someone's snooping now than be surprised when it's Google/Facebook/NSA.