I second the motion. I have a ton of storage on Dreamhost that I could totally be using as backup. (And have tried a bunch of times, but it's a pain getting cron and rsync to do the right thing, and then remembering to set it up again when my computer gets changed around...)
Keep in mind that they don't allow unlimited private backups (they allow 50GB of backups store in a special backup user account), the data you store there is supposed to be web accessible.