I think the main problem here also is that not everyone wants to reveal their social media account (real Facebook account or Twitter account) to the community. So you could not link their involvement on social media to their BM account.
Also, it would mean someone following up on all the involvement to be able to get a reward system going.
That and vice versa. I believe many members prefer keeping their gaming habits more private. Myself included.
That said, giving some minor perks to people who contribute to the game's promotion via social platforms seems reasonable.
