We recently ran into a situation where we wanted to restore one site of many in a Multi-site configuration where the site in question lost all its sidebar widget configurations. Now we want to be proactive and install an automatic back up that allows complete restores for individual blogs on a Mult-Site.
* Checked Vault Press, and they don't support multi-sites: http://vaultpress.com/plans/
* We do backups at the VPS level, but that would restore the entire VPS... not the best option
* We don't want the server to slow way down during back-up times for over 100 blogs