Various technical experts from the DNSSEC/ICANN communities published a paper about six months ago on the problems the remedies can cause for DNSSEC. See http://s3.amazonaws.com/dmk/PROTECT-IP-Technical-Whitepaper-...
In essence, any measure that involves changing the contents of the DNS (by filtering etc.) is indistinguishable from a man-in-the-middle attack which is what DNSSEC is trying to stop.