Wow: Today I reinstalled Dropbox onto my mac and it immediately destroyed my Desktop and my Documents-Folder, after I aborted the sync, because I already have a dropbox Folder on my harddrive. Now I was able to select the proper folder but my workfiles are all gone. This is as desaster... Trash is also empty. That's it for me dropbox. So this is how it feels, when you totally loose control over your data.
Now I just have to wait a few hours for Time-Machine to restore my stuff. Thank you dropbox.