I've just committed a change that allows users with the permission key 'ipblock-exempt' to be exempted from ALL forms of IP blocks, including those which come from DNSBLs.
This permission is by default assigned to the Sysop group, although it can be, as usual, applied to any group using $wgGroupPermissions.
(See bug 3706 and r18904)
How can we on a wikimedia project enable this for a user? There aren't added or changed any Mediawiki messages in r18904.
Hans (JePe)