Oh okay, that explains it them.
Yes, I've been upvoting stories.
But shouldn't it be the other way around?
I mean doesn't that discourage people from upvoting stories they like?
I think it is to reduce frivolous upvoting. Ascribing a cost to upvoting means users will be more choosy with what they upvote – similar to downvoting on SO.
I believe this was part of the idea when Lamernews emerged. In fact, when you upvote you are not really "losing" karma, you are transferring points to the poster of the upvoted news.
Ultimately though, one shouldn't take karma points too seriously :)