People said some things about hard drives being unreliable because sometimes they fail. It's true, they fail, but rarely three at a time. I backup my home desktop/server daily with rsync. One copy on the different local hard drive on the same machine and one copy on the machine I plugged in at school. This works like a charm on my residential Internet connection. If you have a single trustworthy friend and your daily deltas are not in GiBs, you don't even need to drop off the drive. A quick daily glance at the log is all you do for months and years until one of these hard drives fails.

Price aside, every method has it's faults and if something fails some where along the line it's going to be an inconvenience. It's a matter of when that fault happens and how catastrophic it is.

I've used removable optical media for over 10 years now and it's worked very well. Every so often I upgrade the media to new media and keep the old backups stored away. Some people will use HDs and do the same thing, ugprade the HDs when newer cheaper versions come along. I've had some discs fail, but the amount of data lost was small and could be recovered.

At a smaller company I used to work for they would back up their network to hard drives and ship them away. They would keep 3 weeks of backups and rotate through the HDs. After a HD had been used for a set amount of time, it would be retired and new hard drives would be ordered.

I've read about people who would build a NAS, or some other kind of cheap server with a RAID in it. Started out with 4 100GB drives, when it got full they built a second system with 250GB drives, when it got full, rebuilt the old system with 500GB drives...etc etc. That worked great for them.

Depending on how much I need to backup in a month, it could cost me nothing(use DVDs I've already bought) to $40 if I need to add another 400-800 GB.