They key is to never make one service the silver bullet.
For me it's multiple stages of protection.
1) DropBox syncs My Documents so every system I'm on has important files at easy reach and a copy stored "In the cloud" should any system die or get stolen.
2) Manual xcopy batch files that I run once a month to copy the contents of all my computers to an external drive I keep offsite at my parents house. It's two 1.5GB usb drives that I swap with my parents each month when I visit them.
3) CrashPlan+ on every computer in the house that backs up to two locations. 1) Pushed to the CrashPlan cloud 2) Pushed to a external USB drive plugged into my dedicated home server.
As for bandwidth... I'm not pushing EVERYTHING out to the crashplan+ cloud only what I consider high priority data sets. between all my systems I have around 90GB pushed up to the crashplan+ cloud storage but almost 1.2 TB backed up locally. the biggest data set was ~60GB of digital pictures that took about 2 weeks to get uploaded on my 512kb line.
When I write this it sounds a bit paranoid and overkill but it's not that much work to maintain and should be more than good enought to keep me from ever loosing all my data.