What Do You Think of Online Vigilantes?

gwoodrow asks: "I'm a member of the (primarily) Mac community Spymac. I originally joined for the 1 gb of email, but eventually found myself joining in on discussions in the forum. Today, I received an email from a supposedly anonymous Spymac member ("supposedly" because the smart guy didn't mask his IP). Basically, it said that he or she had harvested 10,000 member screen names/email addresses from Spymac's pages and that this, paired with the ability to view individual member's profiles, created a major problem because of the extent of information so readily available. The email this person sent out and the forum discussion that follow are available here. All cracks and personal opinion about Spymac aside, what do Slashdot members think of online 'vigilante' justice?" "Some viruses are released with little notes within that say things like - 'this is why you need to do X or Y to fix your software' Some hackers have also gained infamy by hacking a major system allegedly to help. Do you support such actions and why? Are virus/trojan writers, hackers, and spammers doing a noble deed or going about things in the wrong way? If you don't agree generally, are there exceptions when online vigilantes are fully in the right? Is the accessibility of vulnerabilities a good excuse to partake in such actions, or should there be ethical bounds regardless?"