The same site that I posted about above seems to have gone back to *post* May 17th numbers again today, ie. the bad set of numbers. No changes have been made to the site throughout May and June.
I have to post a correction on this. Google referral traffic is down, but only moderately, and still above May 17th levels. However, non SE referrals have dropped dramatically, almost from every website that is linking to my site. Everything in the top 10 (that's 10 different websites that link to us), have dropped on average 20% compared to even the May 17th week, 30+% compared to pre-17th. I have confirmed this with my own on-server stats software, so it's not a GA bug or whatever.
It looks like other sites are being hit hard today by another round of traffic drops.