I have an 8gb Nexus 7, with >4gb free storage until recently, when I decided to keep a CWM Nandroid backup and a Titanium apps backup in external storage (I had been keeping them, and still do, on a USB flash drive). The Nandroid backup used 1,9gb, and the apps backup used.0 6gb, leaving me with 1.8gb.
I wanted to make new backups, but didn't have enough storage space. Here's where the weirdness started. I found a 3gb file in /sdcard/DCIM. That didn't make sense, since I had accounted for all of my storage. Also, CWM was reportedly keeping 1.9gb of files in both its backup and blobs subdirectories. This couldn't be true, either.
I deleted the 3gb DCIM file - still 1.8gb free. I deleted the 1,9gb CWM backup - still 1.8gb free. OK, it could be the Android unused space glitch... I rebooted - still 1.8gb free, even though I should have 3.7gb free. I booted to the bootloader recovery, and tried a Nandroid backup. It completed successfully, and left me with 1.8gb free storage. I rebooted, cleared cache and dalvik cache - still 1.8gb free. I can live with it, but I am puzzled by the Phantom memory reports.
I later found 0.25gb cached storage hoarded by Google Chrome, which I cleared.
Thoughts and comments?