[A]re we under a moral obligation to use Facebook thoroughly, to represent our full selves? Or, conversely, is it fair to judge people on the basis of omission?Nobody is under a moral obligation to use Facebook at all. But your wall posts do not just appear; they are the product of choices. If you choose to represent yourself in a particular manner, you must accept the consequences of doing so. If you provide your "friends" with no knowledge of your life beyond parenting, it may not be fair to judge you and decide that you must be one-dimensional in real life. But it is fair to judge the decision you made to wall off everything else about you. It is fair to judge you for choosing to represent yourself in a particular way. Your choices themselves reflect who you are. To a certain degree, your total self is reflected even in the tiny pool of knowledge you elected to share.
You picked the role you play. You cannot have it both ways and claim that your circumscribed Facebook identity doesn't show who you really are and that you cannot be judged for the decision to include or omit. (I am not using "judge" in a necessarily opprobrious sense.)
Let us contemplate the words of Lil Wayne:
I don't portray anything, I am who I am. An image is self described.Note the significance of punctuating his last sentence here. Is an image "self-described" or "self, described"? Or both? Perhaps the difference of opinion in this debate lies in which we would select.