I think that groups like LulzSec provide a public service (see "Why the Joker and Not Batman is the Savior of [sic] Us All" http://thisorthat.com/blog/why-the-joker-and-not-batman-is-t... ) in that they show the importance and the need for everyone to be security conscious. I wish there were more groups like this out there raiding and dumping stuff periodically.
I wonder about whether it'd be political or legally feasible to have a law enforcement agency which just trolled around the internet and attempted to crack services that citizens depend upon.
The reason why this is relevant and important to dark nets, is that currently the only folks who use dark nets are folks who have something to hide. That might be folks who are illegitimately persecuted by governments, or folks who are legitimate criminals. These two groups are functionally indistinguishable, even if their intents and causes are different. They both have data they're trying to hide and communicate, without exposing themselves to authorities.