But I recently discovered a trick (I am not claiming I invented it, but I haven't seen it documented elsewhere!) to circumvent this limitation. This is accomplished by the use of symlinks. Let me give you an example - if I want to sync my entire home directory /home/james on DropBox, and my actual DropBox folder is /home/james/Dropbox (but can be anywhere in reality), all I need to do is the following command:
$ ln -s /home/james /home/james/Dropbox/james
This will be a symlink on your local disk but entire full contents (like a hardlink) on Dropbox cloud.
I hope you like this tricks and if you have any comments please leave them below.