Replying to myself after doing some additional testing.
I've now seen multiple examples of Pinterest hosting images with the "original link" being a Google Images search result page, complete with the huge URL query string intact.
While it's possible users who don't know how to find the original URL for an image are pinning Google Image pages instead, the accounts that have pinned them do not look like real people.
It really makes it look like Pinterest is crawling Google Images for specific search terms, auto-generating pages to match the results, and then manipulating Google to get their own pages to show up in Google instead.
I've now seen multiple examples of Pinterest hosting images with the "original link" being a Google Images search result page, complete with the huge URL query string intact.
While it's possible users who don't know how to find the original URL for an image are pinning Google Image pages instead, the accounts that have pinned them do not look like real people.
It really makes it look like Pinterest is crawling Google Images for specific search terms, auto-generating pages to match the results, and then manipulating Google to get their own pages to show up in Google instead.