Unable to monitor filesystemhere's one way to increase the default value of /proc/sys/fs/inotify/max_user_watches at startup, so one doesn't have to do it manually at every boot.
Please run "echo 100000 | sudo tee /proc/sys/fs/inotify/max_user_watches" and restart Dropbox to correct the problem.
As root (or with sudo), create a file
/etc/sysctl.d/30-inotify.conf
with the contents
fs.inotify.max_user_watches=100001
Reboot, or run "sudo service procps start".
That's it!