This feels like I've come in half way through a thread so I'm not quite sure where you're coming from and what's behind your need to make the file permission change.
Having said that, the effect of making the change you mention is that
- Any user can create and delete files in any directory under /home (so if you have 5 users with their own home directories, they will all be able to delete each others' files, for example).
Beyond this the effect depends on whether a user is a member of the group that the dir/file is owned by. Group permissions override world permissions.
For example, if a file runme.sh had permissions 767, owned by user joe and group staff, user joe would be able to execute the script and so would any user not in group staff. Users in group staff would not be able to execute the script (but could still edit it and, if they had write permission to the parent directory, could delete it).
Dangerous? Shouldn't be as long as the users don't have any special privelages and the security is reasonably tight (e.g no SUID files lying around). Secure? Only if allowing all users full access to each others' files is what you want to achieve.