Recently, a hint posted here noted some discrepancies with the Drop Box permissions and permissions of items that are put into it. In short: sometimes a user receives a read-only copy of an item put in his/her Drop Box, and sometimes that item is read/write. Here's why.
To be able to explain what's going on, you need to know a few of the rules that Mac OS X uses for setting file permissions:
Here's where things get interesting. In Tiger, the default permissions for the Public folder's Drop box were POSIX only. So Sally's Drop Box would have permissions like this:
$ sudo chown -R sally:staff /Users/sally
$ sudo chmod -R 700 /Users/sally
$ sudo chmod 755 /Users/sally
$ sudo chmod -R 755 /Users/sally/Public /Users/sally/Sites
$ sudo chmod -R 733 /Users/sally/Public/Drop\ Box
$ sudo chmod +a "everyone deny delete" /Users/sally /Users/sally/Sites /Users/sally/Public /Users/sally/Desktop /Users/sally/Documents /Users/sally/Downloads /Users/sally/Pictures /Users/sally/Music /Users/sally/Movies /Users/sally/Library
$ sudo chmod -R +a "sally allow readattr,readextattr,readsecurity,list,search,read,execute,file_inherit,directory_inherit,delete,writeextattr,writeattr,write,append,delete_child,add_file,add_subdirectory" /Users/sally/Public/Drop\ Box
Mac OS X Hints
http://hints.macworld.com/article.php?story=20081009204908181