When you have ownership issues you cannot change permissions or move files or much anything else. Linux has strict permissions for folders and files as well as programs, etc. When you lose ownership it sets to "nobody" which means no one owns it. Even root (admin) cannot use it but can change the permissions to enable users to use it including themselves. You must to have root access or get someone that has it (your hosting) to do it for you each and every time. 777 servers are not user-friendly for those who do a lot of testing, installing/uninstalling, etc. The reason is that you have to ask your hosting and wait on them to do it each and every time you do something. This is frustrating to the hosting as well as yourself and is probably the number one reason why people change hosting. They blame the hosting for this when it is not really their fault.
777 servers are also not "generally" more secure as 755 ones, although some will beg to differ. 777 servers have to beef up security and 777 means full access to the files and folders while 755 is more strict and does not allow full access. If a 777 server gets hacked, the hacker can "theoretically" gain access to ALL of your folders and files. Using 7555, will only "generally" give them access to the folder and files where they gained access. This means the all of your folders/files will usually not be compromised...only a portion of them.
Why/how does this happen? I have no freakin' idea!
I've never bothered to look it up cause I've never gone that far using a linux server, root-wise. You can't do anything about it if you are not root anyways and I doubt you can even if you are root (not too sure about the last and need to do more digging). This is also why I prefer 755 permission servers. The biggest problem is chown (permissions) which can be easily changed yourself via ssh (really fast, a few seconds, one command for folders and one for files) or ftp (very slow and tedious). SSH doesn't make sense to use on a 777 server cause they will only give you a "jailed" ssh account which means limited access...can move files, etc. but cannot chown which is a root command. In other words, you will not be able to change ownership anyways. :thud:
If you are using 777 servers and do not lose ownership you do not have to worry about permissions as they will automatically change to the correct ones, most of the time and if the folder/files do not have chown issues.
If you are using 755 servers you will always have to change permissions and should do it before installing or uninstalling any mods. Otherwise, something may not have the correct permissions to be edited corrected by smf when installing/uninstalling mods.
Lesson over...time for a pop quiz!!!