Yep, good point - and quite likely if your website is on it's own (non-shared) IP address. One way to work around this would be to create a .htaccess file to redirect any requests not matching your domain name to your own :)
It deflects a lot of blind security attacks..all of which would fail of course, but I don't need that noise in real log files.
This would solve your problem too. If you're feeling vindictive, redirect requests for the offending domain somewhere that will be bad for their SEO.
EDIT: I should add that a null default vhost will exclude HTTP/1.0 clients. But that's a non-issue unless you're serving to very old embedded systems.