Yes. Assume that we are storing crates of sweaty dynamite on top of the servers that hold your important data and design your backup strategy accordingly.
That sounds absurd. And it is; we take your data very seriously. But a good backup strategy assumes the worst, so this is pretty much the only time we'll tell you to assume we're incompetent. If you don't, whatever backups you do—or don't—make are unlikely to help in a situation where we can't.
For sites, synchronization tools like rsync or Unison or version control tools like git can help back up your content. If you're developing your own site, we recommend building it locally and using a tool like one of these to send it to us. That ensures that you've always got the master copy.
MySQL backups are also strongly recommended, especially before undertaking major changes to your MySQL data.
If it's already too late and you haven't made or can't use your own backups, we may be able to help. But as much as we love to save the day, there are no guarantees. It stinks when we have to tell someone that we can't help them get their hard work back. Please make your own backups!