share screenshots with Dropbox does not work
I personally don't have this active on my Dropbox account by default but of you I tried it out on my 10.9 system. 

It doesn't work for me either and this could either be because of the OS or Dropbox. What I suspect is that OS X won't allow the changing of the screen shot location from a third party app. 

What you can do as a work around is the following:

Launch Terminal and use the following syntax:

defaults write com.apple.screencapture location /path/


For example, if I want to have the screenshots appear in a specific Dropbox folder, you would use:

defaults write com.apple.screencapture location ~/Dropbox/Pictures/Screenshots


Log out or restart your Mac and take a screenshot. This should now automatically place the image in the new folder and thus Dropbox is syncing.

For additional fun check out: http://secrets.blacktree.com/?showapp=com.apple.screencapture