There are a few caveats to keep in mind when using symbolic links with Dropbox. First, if you're thinking of linking to your Applications folder to sync your applications between your Macs, don't. Besides Mac OS-specific issues that may arise, there's currently a known issue with Dropbox when syncing of hundreds of thousands of files. (Each Mac application is actually a bundle of many--even thousands--of files, so your Applications folder would easily trigger this issue.) Similarly, don't link to your iPhoto library. Second, don't link directly to a file; link only to folders. Linking to a file can result in the symlink being replaced by the file itself when syncing. Finally, and perhaps most important, if you later decide not to sync a linked folder, be sure to delete the symbolic link only from the computer on which it was created. If you delete the folder from a different computer, the next Dropbox sync will delete the linked data on the original computer, as well, even though the original data isn't located inside the Dropbox folder.