piran, I didn't find/remove any files larger than 50MB, maybe cleaned out 1GB in logs and archives. But 75GB came back to life by itself after letting squid z run for an hour. I can't comment on the linked article other than what I read.
From the article
Microsoft Internet Explorer, Apple Safari, and Opera have no storage limit to keep pranksters from misbehaving. We tried FillDisk.com for ourselves on a Windows 8 machine with updated browsers, and sure enough, our drive started filling immediately
SO, the question is, if a PC is filling its drive, is squid making a cache copy of the crap going to the PC?