We do know - that they demonstrably have abused their powers. I didn't realise it was possible to know about XKEYSCORE with no context or understanding of the Snowden leaks but GP seems to have missed that the "suits" "in charge of XKEYSCORE", the NSA, have repeatedly illegally wiretapped American citizens, to say nothing of the FISA abuses, Five Eyes, etc. Regardless of how you feel about the three-letter agencies' impacts on the rest of the world, the thought that anyone on Hacker News would consider these programs defensible is shocking.

I absolutely do not trust it, but AFAIK the military doesn't feed much intelligence to law enforcement on US soil. (We'll see if that's still the case in the near future.)