Dropbox cannot cross reference your personal photos with your email, your YouTube preferences, your fetishes extracted from your searches, your purchases, your entire location history, etc.

That said Dropbox is another poor choice for privacy. I'm searching for alternatives, but the alternatives don't seem to be that competent, except for the peer to peer solutions like Resilio Sync and Syncthing. My only consolation at this point, until I settle on an alternative, is that Dropbox isn't Google.