After reading the news I doubt the safety of mine and others who use Tor, as one side of the Government is trying to spy and snoop on it and the other side is bankrolling it. Then what prevent the two side of the same coin to join together to share their data and/or know how? In legal jargon this is called "conflict of interest"
We hope and wish that it is secure, but can we prove it? Absolutely not. Let us give it the benefit of a doubt. Now there are so many zero day flaws associated with Tor, Tails, OS, browser, relays, SSL, encryption and the infrastructure of the network that you may think it may not be necessary to make a built in back door. I assume if not all, vast majority of Tor users are already known to government. If you look at it carefully, since Edward Snowden revealed the extent of government spying and snooping, every few months we hear about a zero day flaw, browser flaw, SSL flaw, relay snooping, bridge sent by unsecured email to client and more. So only the naive would believe that they are really secure. Having said that, there are very few things that even provide the level of security that Tor,Tails,JAP(JonDo), and few others will provide. Welcome to the Matrix like world.