I'll let Mr. Topher (<
MacIssues.com> a great site, BTW
) explain it in much better terms than I can. His last point is one that very few of us use: Use a NON-Admin account for our daily activities on our Macs. It's always a surprise to learn that some one in our family, or one of their friends 'messes' with our computer, but it happens. I have to admit I have my wife's MBP set to automatically open her account at Start up; she has enough trouble getting some apps to do what she
thinks they should! She doesn't need the added step of actually signing in to
her own computer!