Iojs removes all copyright headers from src files

"Furthermore, in the event that a work is infringed, if the work carries a proper notice, the court will not give any weight to a defendant's use of an innocent infringement defense--that is, to a claim that the defendant did not realize that the work was protected. An innocent infringement defense can result in a reduction in damages that the copyright owner would otherwise receive."

As each file is likely considered a separate "work" by the courts, removing all the copyright notice is not a good idea.

What they should do is put the lengthy license text in a license file, and then in each work (file) put a two line notice, line one claiming copyright, line two referring to the license file in the distribution package.

Note that the above .pdf also describes "collective works". It is unclear whether a court would consider a tar file a "collective work" to invoke the single notice for collective works option.