Using Subversion with DropBox
My suggestion is to use dropbox together with an encryption tool such as TrueCrypt. In this way you would have a safe storage on the cloud.
SVN works perfectly in a TrueCrypt disk.
If you need to access the repository at the same time on multiple location I would recommend of using a subversion host provider. DropBox can get confused if two persons are modifying the same file at once.
http://wiki.dropbox.com/TipsAndTricks/IncreasePrivacyAndSafety
http://www.randomwire.com/storing-sensitive-data-in-the-cloud