If you're the ROM flashin' type, there's a good chance you have quite a few Nandroid backups floating around on your SD card. While those are undoubtedly handy to have around, they're really only good for one thing: restoring. But what if you only need one specific thing from said backup – like one app, a text message, or your call log? Then the process becomes much more complicated – you have to create a backup of the current setup, restore the old one, backup the needed info, and restore the backup you just made.
How many times has this happened to you: you're getting ready to flash a new ROM, so you drop in on the SD Card, reboot into ClockworkMod Recovery, do a Nandroid backup, and proceed with the installation, only to realize that you forgot to backup your apps. That has happened to me more times than I care to count, and flashing a backup just to do a Titanium Backup is insanely tedious.