Thanks guys. I was asking this only because when I unlocked, rooted, flashed custom recovery, I managed to clear my SD card as well (I wasn't paying attention enough, because I was watching tv show AND having like seventh glass of wine when I decided to start tweaking)
No worries though, because only pictures were important and they were uploaded to Dropbox before. Now I was asking this, because I have backed up my ROM using Clockwork Recovery and I have took backups using Titanium Backups and even though I did download them to computer, I wish they wouldn't be deleted from virtual SD.
As there were options to format
-/data/ and /data/media
I guess that formatting only /data/ does some sort of "delete everything except /data/media"
Edit: I re-installed TrickDroid to get different setup and noticed that it asked if I wanted to full wipe or not. I chose not to, but if I was about to install different ROM situation was different:
Question: Should I always format different mounts (everything else but "/data and /data/media") BEFORE installing ROM and in install process format nothing?