When is it good to be a sponge...?

I'll start off by saying that I wish I could have gone to Cedar City.  While ya'll went south a couple hours, I went north to Logan for a tournament and ended up 3-1.  And because I can't comment on the performance of The Winter's Tale that you saw, guess I'll jump into Act IV of Hamlet...

 Hamlet is crazy as you may recall...  In scene II he is arguing with Rosencrantz and Guildenstern.  There has always been an odd air between them that stemmed from Hamlet's calling them out on their "real" purpose for being there, which is to be the king's stooges:

Ros:  Take you me for a sponge, my lord?

Ham:  Ay, sir, that soaks up the King's countenance, his rewards, his authorities.  But such officers do the King best service in the end.  He keeps them, like an ape, in the corner of his jaw--first mouthed, to be last swallowed.  When he needs what you have gleened, it is but squeezing you, and, sponge, you shall be dry again.

My point is that there's another analogy we use for children; we say that a child's mind is like a sponge.  To me this is a good thing.  A child needs to absorb the world around him and learn to comprehend it's meaning.  I am going to take the stance that we should always have a mind like a sponge, but with filters.  We need to always try and absorb the good, and be willing to share what we absorb.    

Now Hamlet was obviously putting them down; how do you feel about this comparison of connotations?  Is this apples and oranges?  or is this oranges and tangerines....