throw your competitor off Google
To accomplish cache bashing, the attacker uses a link at Google that leads to a cached copy of your company's Web page — as it looked when Google most recently indexed it. Your nemesis then posts the copy of your page somewhere on a site that has a higher "page rank" at Google than your site does. Because Google eliminates from its index any pages it finds that are simply duplicates of other pages, your company disappears from or is strongly penalized in Google's rankings.
Since a cache-bashing attacker gets copies of your pages by visiting Google's own cache — not your site — banning offending IP addresses no longer works
the only defense at this time is to configure Google not to make cached copies of your Web pages available. This is simple to do, as explained in Google's help file.