Default Dropbox installation includes downloading and installing Nautilus extension first. It will add Dropbox icon/application link. When this is run for the first time, it will download and install proprietary daemon. However, on a slow link this download often fails if I use the connection for parallel downloads. Running it again will not continue the download but will download again from the start.
To download the daemon manually, we can run the following command:
cd ~ && wget -O - "https://www.dropbox.com/download?plat=lnx.x86_64" | tar xzf -
Note that I'm using 64-bit version in the link above. Official instructions are available here.