Also Snowden was certainly aware of the fates of previous intelligence leakers like Thomas Drake[0] and William Binney[1] and others who tried to blow the whistle through the proper channels, only for nothing to happen.

[0]http://www.smithsonianmag.com/history/leaks-and-the-law-the-...

[1]http://www.computerweekly.com/feature/Interview-the-original...