The ".Sony" folder name only causes a minor problem on systems running System 6 or earlier. It is definitely not a problem with systems running System 7 or higher. Under any circumstance, naming a folder in this way will not "trash" or otherwise corrupt the data on the hard drive.
The cause of the problem is the way the System 6.0.x and earlier file systems dealt with files and drivers. Opening files and opening drivers used the same toolbox routine. The system would look at the name of the "file" and if it began with a period, would send the open call to the Device Manager. If the file name did not begin with a period, the call was passed to the File Manager. Unfortunately, ".Sony" is the name of the floppy driver so trying to open a file with this name will confuse the system.
Naming a folder ".Sony" should not cause a problem on any Macintosh computer, no matter which system software is running, since only the Finder itself "opens" directories and that is not done with the an "Open" call. The Finder simply searches the catalog file for the names of files and folders whose parent ID is equal to the ID of the folder. No files are actually opened.
In my testing with System 6, I created a new file in TeachText and tried to save it with ".Sony" as the file name. The file would be created but TeachText said it could not open the file to save the data. I tried double-clicking the file and TeachText would launch but I still received the error dialog stating the file could not be opened. I could not trash my hard drive as stated in the MacWorld Secrets book. I could not duplicate this problem under System 7 at all.
Support Information Services