My guess would be mounting an NTFS partition - with ntfs-3g it will load everything as 777 just by default, since it can’t translate the permissions.

I've seen users who have every file set to 777. They do it to "avoid permissions issues"

Well, everybody has 1777 as /tmp (with the sticky bit).

  $ ll -d /tmp
  drwxrwxrwt. 20 root root 4096 Mar  3 12:19 /tmp
  $ mkdir mytmp
  $ chmod 1777 mytmp
  $ ll -d mytmp
  drwxrwxrwt. 1 luser lgroup 0 Mar  3 12:19 mytmp