It also gets lots of people on the record making claims about the capabilities of the NSA and how much they are really collecting. Many of these people are on the intelligence committee and have been fully briefed on everything the NSA is doing and they use those credentials to support their claims of authority.

Glenn Greenwald says that he has hundreds (if not thousands) of documents, including NSA training manuals, that prove Snowden's claims about NSA analysts having the technical ability to listen to and read the contents of "billions" of phone, email, and chat conversations. See his response starting at 19:51 in this interview:

http://www.democracynow.org/2013/7/18/glenn_greenwald_growin...

Senator Wyden's recent comments support the idea that there is much more coming in this story.

http://www.americanprogressaction.org/events/2013/07/16/6975...

It is incredibly hopeful that there is this much support for an amendment like this before the full story has been told. I hope the Senate is forced to take up a similar vote (less likely for sure) before the full details are published because it would be very valuable to get the position of every Senator on record before November 2014.