Back in the day, I tried out the .Mac service. (I think that I got it as part of a deal as a content expert for the Apple Newton system.)
Mind you, this was in the days of 12,000 baud modems for most of us, and online connectivity was not always the most certain of processes. However, I found that, just when I would need it most, something would always go wrong and I would be unable to access the content stored on the server.
Since portable storage has gotten more and more portable and more and more affordable, I've given up on the idea of the single ("always accessible") system, and instead have gone for the three backups (one on board the computer's hard drive, one along on a hard/flash drive, and one in the famous "secure location", sitting there next to Dick Cheney in the bunker.
In the last year, I've purchased a tiny little thumb drive. literally not larger than 1 1/8" by 1/2" by 1/16", that holds 2 gigantabytes. It's so small that you really have to worry about it slipping into a crack somewhere, and I take precautions to keep it in that "secure" location in my traveling stuff. While it's not up to backing up huge photos or sound files, for critical data materials, it gets tucked away in the luggage away from the computer stuff.
But boy, oh boy, does it get hot when you are accessing the contents...
