Safari Reset function - couple privacy questions


Ministry of Re-Education
First of all, can this function really reliably remove all existance of one's web activities? Can it be reversed? Can someone with an extensive IT background dig up the reset info? Is there anywhere else someone could find web access logs, url's, etc. indicating internet activity?
If you use a proxy server or some sort of software server for internet access, then your actions could always be traced in the logs on the server.