[sabat]

This could almost be done (on Linux at least) with a copy of rsync, git (for the revision control) and a shell script.

Er, well, yeah, but you'd be polling almost constantly if you're trying to emulate what Dropbox does. I don't know exactly how Dropbox knows when I add or change a file -- I assume it ties in to the kernel. Also, rsync wouldn't work over HTTP, which is a big disadvantage in some of the environments I've been working in lately.

My big question, though: why isn't someone doing this for headless servers? Why do they always assume people just want this for desktops? At least you can hack a headless version of Dropbox on Linux.