Lame_Wolf - 9:13 am on Nov 1, 2012 (gmt 0)
I have spoken to Pinterest about this. Paraphrasing here...
If you provides a valid DMCA notification, but do not use the form, Pinterest assumes that person is asking for site-wide removal and to assign a strike for purposes of their repeat infringer policy.
I am still waiting to hear back on further questions that I asked.