Just did a whole format and reinstalled OS X up to 10.2.6. In my initial installation, I somehow didn't notice the entry for my short name as administrator. After full installation, I see that my full name was in place for my short name. According to David Pogue's book- The Missing Manual, your short name is supposed to be 8 characters or less. OS X installer is also supposed to suggest a variation of short names derived from your full name. I don't remember seeing any of that. Nevertheless, OSX is running fine with my "full" short name, but should I expect any problems in the future?