3Authors opinion inserted here: I am not very enthusiastic about lookaside validation
Since anybody can, in theory, start a DLV registry it will very difficult to know who to trust and to get a full picture of which zones are secured and which not. On the other hand it is a mechanism to provide early deployment maximum beneﬁt. At some point this section may disappear from the HOWTO.
At the moment of writing the author advises to use ISC’s DLV registry.