Polonius, Polonius, Polonius...what to do about Polonius?!? I have to say that my gut reaction, putting aside 21st century morals and beliefs as much as I possibly can, is that he did deserve his death. He made the choices he made - He put his daughter in harm's way (at that point people were saying Hamlet was crazier than a loon, but Polonius offers his daughter to Hamlet, saying, "Oh, I'm sure he's just acting like a mental patient because he's SOOO in love with Ophelia!"); he sent spies out to keep tabs on his son (even though his own behavior was suspect)...ultimately he made very poor choices that led to his demise.
Probably for me, the biggest reason I say that he deserved it is because of his treatment of Ophelia. Claudius was NOT pushing him to make Ophelia the reason for Hamlet's madness. At no point did the king or queen say, "Hey, Polonius, we would like you to see if Hamlet's is insane because of your daughter." Polonius made that choice because (I believe) he wanted to see an alliance between his daughter and the prince. What better way to secure his position at court and his fortune?
Polonius got what he deserved - Hamlet said it perfectly when he called the person behind the arras a rat.