Why it’s so bad
First it disables your middle mouse button; second it disables your right mouse button, if that’s not bad usability I don’t know what is. Now you can no longer open links in new windows via middle click or right click. You can’t access your right click menu, which also means you can’t use the built in spell check some browsers have when filling out the websites contact form to complain about this terrible script they are running. The only thing you can do is left click your away around the site and if you cease this behavior you will get a punch in the face message that basically tells you not to steal their content. Thanks for assuming the worst and insulting me at the same time.
Who are you fooling?
So you have thoroughly annoyed any power user by now, but not only have you annoyed some of your visitors you aren’t protecting anything. Anyone who is even remotely computer savvy can take a screen capture of any page on your site or even save the page. A slightly more savvy user will just use the only remaining left button and drag the image to the address bar and bang, the image is loaded all by it’s lonesome ready for the taking. An even more technically minded person can just view your source via the view source menu and take your code, content or images and do as they please with them.
This is just the tip of the iceberg. Chances are your site has been indexed by hundreds of crawlers many of which are the ones most likely to steal your content in the first place. Your copyrighted images are probably showing up in paces like Google images too, so do us all a favour and get rid of the ridiculously annoying script. If you happen to be the victim of one these sites take two minutes and find the contact form and fire off an email informing them of their ill ways, or better yet, send them this article.