Hmmm, I now feel we're at a "What's your price?" level of agreement (the old "Would you sleep with me for a million pounds?" joke), in that I agree 1,000+ points for forwarding an item is beyond ridiculous (and for something like that a "please drop my karma" option would be worth it ... although I'd assume 1,000 point boosts are very rare).
Your case of a bit over 50? Out of proportion, very possibly (I don't pay close attention to this level of detail), but maybe not "totally".
Then there's the "this rewards one for other worthwhile items forwarded that got lost in the crowd" theory. For those driven, at least in part, by a desire for more karma, this encourages them to continue to forward worthwhile things. If it encourages them while not discouraging you from continuing to forward items....