@kizmark
If you block it via .htaccess, it will be blocked for that site only, e.g. root/domains/somedomain.com/.htaccess
But the user will be able to access root/domains/someotherdomain.com as his ip isn't blocked from accessing the server, just from accessing the specific site.
If you block it via iptables, guy with the blocked ip won't be able to access any site hosted on that server..
Nice. Thanks Jason