Protecting Intellectual Property:
Much of the content that Snowden sent to Glenn Greenwald was highly classified, including material at the Top Secret classification level. This is why Snowden’s actions were highly controversial, with some calling him a hero, and other a traitor.
Opponents of Snowden’s actions argue that his actions put national security at risk. Some argue that he didn’t properly redact some documents, leaking information that had no relevance to his cause, but caused damage to national security. [Need to cite this, can’t find the source at the moment.]