"Certain files in this folder cannot be shared due to a takedown request with the DMCA"
I interpret that as he has some copyrighted files in his private folder which he is trying to make shared/public. Perhaps dropbox has previously gotten a takedown request for those files (when shared by some other user), and to comply with the request is preventing anyone else from sharing the files in the future.
Besides, what might be copyright infringement to one user might be legitimate usage to another. For example, you might have an illegal copy of an ebook in your folder, but I have the same copy, but mine was paid for. Should I lose access to mine? OReilly books don't have DRM, so it's possible it could happen.
While technically true, I think it is very rare that a file is DMCAd for one user while another is sharing it legitimately. Rare enough that a trip to customer service is warranted.
> For example, you might have an illegal copy of an ebook in your folder, but I have the same copy, but mine was paid for. Should I lose access to mine?
Note that the discussion here revolves around sharing, not having personal access. So while you should (and would with Dropboxs current system) retain your own access to the files, you shouldn't be able to share it, which seems reasonable to me.
The message is quite cleverly constructed, as it doesn't actually say that there is a DMCA takedown request against the file (because there isn't). It just says that there has been a takedown request sometime, possibly(probably) against some other file/url.
However, as stated, the DMCA isn't currently meant to take down the file and keep it down forever. It's meant to kill links one at at time.
Bigger organizations want it to take a file down and keep it down forever, which is what's being kicked around now as being a possible reinterpretation of the DMCA, which is crazy.