Could this be another database/algo flaw ....
or a sweeping policy change that has many false positives?

A sizable number of whitehat websites and blogs have just been dropped from the results. There does not seem to be any noticeable pattern.

Can you name some of the blog URLs?

Always have been concerned about embarrassing specific Bloggers or Webmasters

But hopefully, others may chime in with their own stories if they wish

No this wasn't probably a flaw. This was a google crackdown on sites engaged in buying and selling link power. This was expected since the same was done with link selling directories as well..