AndrewC: A bit off topic, but you know how your browser asks you "Remember the password for this site?" and your options are "Yes", "Not Now", and "Never?" Most people don't really think about this, and click "Never" when they're doing something they're not supposed to be doing. Well, how do you think your computer can REMEMBER to never ask you again for that site, WITHOUT KEEPING A RECORD OF WHICH SITES NOT TO ASK YOU ABOUT?
Ding ding ding ding. So, if you're busily telling it "never remember the password for this site" and thinking that means that nobody can ever tell you go to loads of pron sites, you're doing it WRONG, WRONG, WRONG - because now, not only is there a record of these sites in the browser history, there's a much more incriminating list - which generally doesn't go away when you delete your history - which demonstrates that you have not only been to these sites, but that you are in fact a member of these sites.
Why again should I be concerned? Is my password stored in my browser? Nope so where's the danger?
As for your hiding that you go to loads of porn sites if your that worried, don't become a member on said sites. Problem solved. Unless an average person going on your computer has some advanced techniques, they'll never know. Someone is clearly paranoid.