...There is no point in hoarding sMerit; keeping it yourself does not benefit you, and we reserve the right to decay unused sMerit in the future.
From any signature-camp participant perspective: not sharing points benefits me, as I make it harder for new ones to rank up and become a competition for me, making it easier to get the spot in campaign and could keep payment rates higher. It also increases the value of my account.
If someone is only concerned with sig campaigns and/or account trading then yes, there are probably ways to abuse the system. Hopefully the overall impact will reduce spam sufficiently to outweigh potential negatives but this may take a few weeks to settled down. Once the initial sMerit bonus is gone we'll start seeing how this actually works.
If you are seen to receive a lot of Merit but not send out Merit yourself, peole would stop sending Merit to you, as that equals burning them.
Eventually, you'd be stuck with those sMerit you have aquired at the beginning, while everyone is participating in rewarding posts.
Or in other words: you'd lock yoruself out from the merit system.
(This assumes the majority of the people participating behaves in a responsible way)