>you can already build such a system yourself quite trivially by getting an FTP account, mounting it locally with curlftpfs, and then using SVN or CVS on the mounted filesystem.
There's no way I'm turning kids loose on a spreadsheet to tally their votes for a Disney vacation.
I didn't include that kind of users, because I'm not travelling with them. Just like you I wouldn't trust them with the main spreadsheet, but surely you can give them their own spreadsheet: they won't be participating in most decisions anyway, so it's not like you'll need to copy paste most of it
There's no way I'm turning kids loose on a spreadsheet to tally their votes for a Disney vacation.