They found that backup in realtime caused the virus or damage to propagate to the backups. That's why most just image or copy the HDDs on a schedule. There are sync apps that I use when I feel like its time for my work in progress.
I currently run a business on my Win7-64 machine and want to have some kind of system that can be basically switched over in case of a failure. I'm not really looking for backup solutions as I already have a small NAS that does that to some extent. I want something that does real time mirroring to another machine whereas I can basically start up either PC and see and do the same exact thing with the same system, programs, drivers, etc. Does such a thing exist? If my computer does go down or a bad C drive say... I would have to reinstall Windows, re-install probably over 100 programs, etc. It would be a nightmare.
On my PC I run tons of programs, 6 printers, 2 scanners, dual monitors and also run a small non-public web server (xampp) to do my back end stuff. Fairly heavy duty stuff.