Yes, we removed this, for the reason mscott mentioned.
But if you whitelisted Canada and USA and you are from one of these countries you can enable it to block other countries:
INSERT INTO `sys_dnsbl_rules` (`chain`, `zonedomain`, `postvresp`, `url`, `recheck`, `comment`, `added`, `active`) VALUES
('spammers', 'zomgbl.spameatingmonkey.net.', 'any', 'http://spameatingmonkey.com/index.html', '', 'This zone is guaranteed to block 100% of all IPs because it lists everything (0.0.0.0/0). Use it only if something is whitelisted.', UNIX_TIMESTAMP(), 0);