Should this error be included in bad id along with the original "deleted post" error? Up until now, I've been leaving these posts alone, neither removing nor adding bad id.
(I'm leaving out the MyPicks error since at least with that you can still access the artist's profile.)
I've finished my second scan since then, so here are my records on bad pixiv id added/removed by my scans. The dates mark the starts of the scans (beginning of the month). I didn't keep records prior to Oct 2010. May 2012 is when I started treating private images as bad pixiv id as described above.
(The results of future scans will also be put here.)
Now I'm considering adding the MyPicks and suspended account errors to bad id, simplifying the definition to "any pixiv post that is no longer publicly available".
Switching from parsing raw HTML to using the Pixiv API (like used here) near the end of the Sep 2012 run ramped the rate up to 250ppm. Posts from suspended accounts don't show up differently when querying specific images (you have to request all images from the artist to see the error), so I won't be able to automate bad id for those, but whatever.