Do you discourage keeping SMF database in free web-based storage sites? Just in case the hard drive or external drive fails, at least one still has the back-up (aside from webhost backup).
its always a good idea to save a copy of your current database and files
It depends on the policy of those sites. If there is no authentication, then someone can stumble on the file and they now have all your user information. Sites like Rapidshare, etc are bad ideas for storing backups of information like this.
In my opinion, it is generally best to have your backups on a system you fully control like your local computer. Lacking that, a secure file storage site might be another option.
I saw a list of free storage sites in Mashable. I need to read each site's TOS and will decide which one is more secure and reliable.
Maybe an updgraded account will work best for me.
I just want to have multiple back-ups of databases.
Why not just buy a USB flash drive. You can get a 2GB Kingston for $15 shipped from Newegg.com. Cheap insurance for your site. No need to rely on a hard drive. Although just make sure you don't loose the thing. ;)