UPDATE: 3 days later, ma.gnolia launches http://recovery.ma.gnolia.com. It just re-formats FriendFeed's feed into CSV and Bookmarks HTML. The big problem with this is the loss of tags so it'd be better if they could recover from some backups ...
So I'm extremely weary at the use of the term "cloud" in reference to anything other than the fluffy white marshmallows of the sky, and today's ma.gnolia.com outage is a timely reminder for everyone to keep backups of their data. But its not exactly the end of the world.
Yes I have a few private bookmarks that might be lost (but hey, who knows what ma.gnolia may recover), but for the most part all the stuff that was shared has been mirrored into the 3,178,983 social aggregators out there.
For example, FriendFeed has my entire collection of public ma.gnolia bookmarks, conveniently in a parseable format.
And because FriendFeed feeds into my Facebook, there's a second copy there. Oh and also in MyBlogLog. Free backups = win.