Why CodeIgniter says having a directory with 777 permission to use file uploading class?

[eluser]Unknown[/eluser]
Hi.
I've heard web developers should not have any directory with 777 permission on their websites because it creates security problems. But why does CodeIgniter ask it in its File Uploading Class documents?

[eluser]InsiteFX[/eluser]
See the PHP.net CMOD