I think it was just down while the NSA were installing their beam splitters and PRISM Panel.
From what I saw, WWDC had been over for quite a while before HN went down.
Second this. HN was running perfectly fine, with some relatively quiet WWDC threads, quite some time after the keynote ended. Apple's Developer site went down at the same time.
Yes, but my guess the highly trafficked comment pages and perhaps the high activity on the database might have taken it down.
PRISM + WWDC -> very high traffic. Just speculating.
Correction: PRISM + WWDC + E3 -> very high traffic.