Recently there's been mention of making "world-writeable" directories, ala the auto-recover directory for Word, and this recent mention of a particular Adobe application.
If folks are merely using the Finder to do that, I humbly suggest you're opening (huge) security holes!
There is another method, using a shell (Terminal window) and the chmod command, that will invoke the "sticky" bit in the UNIX file system. Instead of the customary "chmod 777 whatever" try "chmod 1777 whatever."
That leading 1 will enable a very useful feature when dealing with directories, which will prevent folks from modifying files that are already there if they're not the owner. Anyone can create a new file, but once created, that owner is the only one that can modify it.
We do this here at our school with a particular directory shared by the students in the video production classes.