Since it seems that despite all the voting to get dropbox on the FS we are not getting much back, I thought I would let you guys know about a possible alternative: http://ftpbox.org/
FTPBox is supposed to work just like dropbox, but using a simple FTP or SFTP server as the backend. In other words, a simple OpenSSH install would be enough.
The project is quite young, and there is only a Windows client, but it seems very promising. Certainly something to keep on the radar.