At some point you may switch to a different OS and that OS might not include Gnome. If that is the case, then Nautilus is probably not the file manager either. I ran into this recently while running Xubuntu on one of my systems.
After googling around for a few, I came across another great blog that already had the answer. http://antrix.net/journal/techtalk/dropbox_kde.html
I simply added /home/himuraken/.dropbox/dropboxd to my startup and it is working great.
–Himuraken