Like I said above they can't upvote each other. Because they need the initial upvote from someone who is already "in the system" (ie. at least 2 karma) first.
So at least one of them has to say something that the original community finds useful. And if he/she does manage to upvote his friends, those upvotes will generally be cancelled out by the community (not because they are fighting spam, but because they don't agree with the upvote)
So at least one of them has to say something that the original community finds useful. And if he/she does manage to upvote his friends, those upvotes will generally be cancelled out by the community (not because they are fighting spam, but because they don't agree with the upvote)