The images are on your URL and you domain (in most cases).
So you get the DMCA regardless of real ownership -- That simple.
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The whole process is corrupt.
Google just accepts their bullshit without question because they will have no legal liability in doing so -- Google does not care. Actions speak louder than words -- always.
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A lot of good shit in this thread -- this bullshit has been going on for years.
https://news.ycombinator.com/item?id=8848544
===This is not a recent issue -- abuse of the DMCA process
If you cannot face your accuser how would you know if there are other mass - DMCA frauds from the same source. The US 6th Amendment only applies to criminal law -- criminal. US laws are not admissible in foreign jurisdiction except by treaty.