No NSA fan myself, so I'm not going to defend them. Snooping on Americans' phone records was definitely a violation of the right to privacy, among others. The good news is that it's over now
Perhaps now we have one more reason to avoid voice calls through phone and do that through Whatsapp or other VoIP services. Since they are encrypted, I don't think that anyone can snoop them (unless someone physically manages to install spyware on the phone). In this case they have done that to the terrorists, but I am sure that there may be other incidents, when this was done to law abiding citizens.