Seeing as dropbox stores the file local, you will not have any problem with mounting it simultaneously. You couldn't merge the changes, though. The bigger prob

Seeing as dropbox stores the file local, you will not have any problem with mounting it simultaneously. You couldn't merge the changes, though. The bigger problem would be to access it e.g. on your iphone/from the web. For that reason, the webservice should be able to serve an unencrypted part if you enable that functionality. upon providing the passphrase, of course and waiting for the decryption. that could be a special feature which costs more, but would definitely add something special, which others do not provide as of now.