Online backup is a wonderful thing, but you can't assume it will always be there. Use these services to protect yourself but don't become dependent on them.
ExtremeTech.com: Firefox is the cloud's biggest enemy, 2011-Oct-28, by Sebastian Anthony
The browser is the portal through which the entire web is experienced, after all. In actuality, cloud-based computing represents a serious conflict with Mozilla’s primary purpose. In the words of Mitchell Baker, Chairperson and Chief Lizard Wrangler, Mozilla’s mission is to “build user sovereignty into the fabric of the Internet.” User sovereignty means that you are in full control of the surfing experience — it means that you are in the hot seat with regard to how much information you share and with who. User sovereignty literally means that the consumer is king and should never beholden to any other user or corporation on the web. You can see how this doesn’t really jibe with the centralized, all-your-data-are-belong-to-us aspect of modern web usage.