None of the above will help a pinner in court.
- I didn’t make any money from the infringement.
- I didn’t know it was copyrighted.
- If it’s on the web, then it’s public domain unless clearly marked otherwise.
- I gave credit to the photographer.
- I took it down when asked.
Especially if the pin board is decorated with the "disclaimer" no-copyright-infringement-intended-none-of-the-pictures-are-mine.