I'm not sure most people lose sleep over being defriended on Facebook . . . it's like, "Oh no, my old coworker from 1998 doesn't want to look at my vacation photos anymore! How will I survive?"
But if you do worry about it, researchers with LiveScience at Arizona State University used focus groups and studies to come up with these ten SCIENTIFICALLY-PROVEN rules to keep people from defriending you on Facebook. Check 'em out . . .