I never promised it was a cure all, and yes I'm sure that someone with enough technical nouse could hack your site before you even noticed, regardless of anything you've done.
However, what it will do is track the significant number of amateurs who're just "having a bit of a laugh", and allow you to block them, report them to their ISPs, etc. Plus, what Neil says.
No, it wont track the hacker deeply enough to let you phone them at home and quote their shoe size back at them, but it gives you another tool to try to keep them away.