Philip Agee and Edward Snowden: A comparision.

Links to articles (Wired one is behind a paywall):

CIA Diary – Inside the Company (Excerpt)

Snowden – I Left the NSA Clues, But They Couldn’t Find Them (Full Interview)

Related:

Snowden and the Ethics of Whistleblowing

Snowden also explained to Greenwald how his leaks differed from those he had previously criticized. “When you leak the CIA’s secrets, you can harm people,” he explains, as Julian Assange’s more indiscriminate Wikileaks had, perhaps, demonstrated. Blowing the whistle about NSA surveillance supposedly would not harm anyone: “when you leak the NSA’s secrets, you only harm abusive systems.” As Snowden has repeatedly emphasized, he meticulously sorted the secret materials he released with an eye toward minimizing danger to others: “I have carefully evaluated every single document I disclosed to ensure that each was in the public interest.” Snowden encouraged Greenwald to filter the leaked materials so that they could reach the public “without harm to any innocent people.” Rather than place classified materials online in bulk as Assange has, Snowden urged a more cautious approach. “If I wanted the documents just put on the Internet en masse, I could have done that myself,” he tells Greenwald.