So, it looks I could be right when I said a few days ago:
And that more anti-link-exchange changes could appear recently. Yesterday I looked at Matt Cutts' blog and what do I see?
Look at "indexing timeline" post.
"I’d think about the quality of your links if you’d prefer to have more pages crawled. As these indexing changes have rolled out, we’ve improving how we handle reciprocal link exchanges and link buying/selling."
(no, that wasn't about my site)
Nobody said that, so I will: I was right :) Are there any awards for that?
Simply the more percent of your links are reciprocal, the bigger BSR ("Black Seo Rank", my own name:) you get. The same with simply linking to "bad sites" (with high BSR), even without back links - in other words linking to bad neighbourhood. And now G simply detects it more accurately.
Oh, and did I mention that I was right? :)