My colleague Alexis Madrigal has a nice primer up on Wikileaks. Following his leaks I came across this Wired piece on former hacker Adrian Lamo, who evidently, dimed Private Manning out. I have to admit my visceral reaction was negative, but as Lamo outlines the case, it seems clear to me he did the right thing:

Lamo has contributed funds to Wikileaks in the past, and says he agonized over the decision to expose Manning -- he says he's frequently contacted by hackers who want to talk about their adventures, and he has never considered reporting anyone before. The supposed diplomatic cable leak, however, made him believe Manning's actions were genuinely dangerous to U.S. national security. 

 "I wouldn't have done this if lives weren't in danger," says Lamo, who discussed the details with following Manning's arrest. "He was in a war zone and basically trying to vacuum up as much classified information as he could, and just throwing it up into the air."