How many players that can win 0.0025 btc? There is no stated any winners there and how are you going to determine the winner? By random pick? I think it still can be abused as well though because people can make many facebook account just to farm it easily not to mention they have real friend there or not
It is a common thing, there will be always abusers when there is giveaway. If there is only 1 winner then abusers will be able to increase the chance to win, but it will be bad if all who are commenting on the post will get 0.0025. Actually when it comes to social media promo, abusers may help to promote the site because each account may have different friends.Of course it will always depends on how they manage the promo. If there is no restriction of the facebook account such as minimum number of friends then it will not be a good promo for the site.