None of this, none of it at all, has anything to do with what happened to ...
Nice try again, but this is directly addressing something else altogether. It seems to show, that you most likely have never personally handled information at this level.
You're just wrong to think unless something is "TOP SECRET" and a government document, its not a "leak" in contemporary usage.[1] YC's email that ended up public was not meant to be public, however you want to debate the wording. It was provided here only as an illustration people are familiar with. There is no opinion expressed here about the situation, nor implied (its been discussed by PG on numerous threads).
There are well-trodden notions of confidentiality, privlege, and confidence outside of govenment. Things that are familiar to people operating at the level of founders, vcs, board members, etc. If you are't familiar with this, that would explain some of your comments. You were the one who needed a citation. Here is a typical excerpt:
Most other folks are too nice to actually mention it, but since I'm not a VC or big deal business tycoon, I'll just say the most important point outright: Asking for someone to sign an NDA also often makes you look amateurish. -- Anil Dash
But, that would genuinely surprise me, to the extent I almost don't believe you would not be aware of this. I'll be charitable and assume you mis-read or mis-interpreted what I wrote. It seems most likely you mis-inferred something about what may or may not follow as a result.
For this reason, you'll note there are [now] more footnotes and citations, for the benefit of others. [This was one]. Some of these were added after you made initial comments -- I'm happy to take advice to make things clearer -- and I happy to aknowldege these changes.
Citations: On NDAs an etc.
....
Why a VC Will Take a Lighter to Your NDA - Wilson Sonsini
http://startuplawyer.com/venture-capital/why-a-vc-will-take-...
Why Most VC’s Don’t Sign NDA - Foundry Group
http://www.feld.com/wp/archives/2006/02/why-most-vcs-dont-si...
One More Time: No NDAs - Anil Dash
http://dashes.com/anil/2010/05/one-more-time-no-ndas.html
From PG: YC Library http://ycombinator.com/lib.html
The Cult of the NDA.
tl;dr "Cases where trade secrets and/or patents are both protectable and essential are rare."
http://www.frozennorth.org/C509291565/E1939404619/index.html
.......
Lots of communication happens in confidence, but not under NDA for various reasons.