Replication is not backup either!
Ditto on the comments about raid, but simply using rsync or other techniques to copy your files to a remote drive isn't a backup strategy either.
What happens when the file you just copied turns out to be corrupt? You need an older version.
How many older versions do you need? In one case where a telco killed their system, they had to go back 14 MONTHS to find data images for a phone exchange that weren't corrupted, then wind in all the incremental changes over a 4 week period. Meantime 90,000 people had dodgy phone service (I was one of them)
Home backups are a pain in the a***, primarily because of media fragility and where to keep it safely (backing up 1Tb+ onto DVDs is a no-go, big tapes are pricey and hard drives are touchy)
For $orkplace I use Bacula, but I'm backing up several tens of Terabytes with it and have all the right gear (tape robot, fibre, giant data safe, blah blah etc ) to go with it.
Bacula's fairly simple to setup for home use. It doesn't have a whizzy gui and you need a propellor beanie to set it up, BUT it works really well.
The online services seem like a good idea, modulo the question of "can you trust them?" - encypting your data BEFORE it goes upstream might solve that though - but you still have the issue of blowing your data cap every time you make a full backup. :(
Mine's the one with the tinfoil beanie in the shoulder pocket.