Just a quick post on something that has been annoying me for a few days.
I recently installed Ubuntu 13.10 and couldn't get the Dropbox sync program to work. After much hunting for information and a bit of trial and error I have found a solution. My problem was that after the install the Dropbox program would say that my computer was not linked to an account, but gave no option to add an account. In past installs the Dropbox program would throw up a dialog after installation to enter your account details, but on my 13.10 install it did not.
My solution was to uninstall Dropbox and then reinstall using the instructions here:
Once I ran the script at step 7 the add account dialogue box popped up and now everything is fine. It also seems that the the dropbox notification indicator is broken (doesn't show) in 13.10. To fix this install package libappindicator1 then log out, and then log back in (or issue dropbox stop && dropbox start at the command line).