Advertising is kind of an important cultural artifact. Sure, we discard a lot of it almost immediately, but it is designed to speak to us right now, being relevant in our everyday lives, in a way that fiction, official history and big governmental mandates do not. Tomorrow's historians will know about our everyday lives to a large extent because of the advertising we leave behind. The only other thing as relevant is our person-to-person communication.
In summary, the important historical artifacts you are now leaving behind are your spam folder and your email inbox.
Mokalus of Borg
PS - And your social networking profile.
PPS - And I'm sure that's just the start of it.