Daring Fireball points out an interesting post about family use of an iPad. Others have already talked about the difficulty of sharing iPod Touches: what if two people have different desired sets of apps? Or different sets of high scores on the games?
If Apple can make a simple way of "switching users" for the iPad and iPod Touch, they could easily become family tablets. I propose that passwords be optional, and parental controls of some sort be part of the picture. This could be done on other brands of tablets, of course, but I suspect that Apple will do it better than a typical Android tablet supplier.