A protective resistor in series with a microtip is known to homogenize field emission. It is not widely recognized, however, that this protective resistor must be fail-safe as well, since the microtips are exposed to rare but potentially destructive events during life. This article addresses two proposed protective resistor concepts : (a) a vertical resistor located locally underneath each microtip, and (b) a lateral resistor radially distributed from the center of each microtip. It is shown by electrical and thermal analysis that the lateral resistor is significantly more fail-safe than the vertical resistor by factors of about 10X and 100X, respectively.