It's not a simple mistake, it's the result of using dumb automated systems without caring in the least if it affects anyone else. In the past they've already sent DMCA notices about news articles[1] and to takedown notices themselves[2].

[1]: https://www.techdirt.com/articles/20120525/01520819073/fox-i...

[2]: http://www.myce.com/news/dmca-takedown-notices-run-amok-than...