The Android and iOS mobile clients don't currently use HTTPS for transferring meta-data, but do for file contents.
ecryptfs isn't a suitable alternative to my suggested solution which would involve all Dropbox clients having the capability built in. Of course, people who are really paranoid can use their own layer of encryption on top as well/instead.
Fair enough, but having something built in to Dropbox for people who value convenience wouldn't prevent anyone from using solutions like ecryptfs as well.
ecryptfs isn't a suitable alternative to my suggested solution which would involve all Dropbox clients having the capability built in. Of course, people who are really paranoid can use their own layer of encryption on top as well/instead.