You can hide anything you want it won't break anything, but obviously you won't be able to access anything you hide from the EZ5's menu. Any programs on the cart that can read or write to the microSD (eg anything DLDI enabled) can still access hidden files/folders though. For example, I have most my GBA games in a hidden directory as I use Rudoplh's 3-in-1 tool and that way they don't show up until I use said tool.