The value of a point
intelligent-conversation.blogspot.com
intelligent-conversation.blogspot.com
Seriously, if you post something that provokes really good (useful, whatever) comments, you've done something good for the community and a positive reward for that is hardly unearned.
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....