If it's cheap enough, it'll be just like email spam - basically everywhere worth influencing in any way will be flooded. And it'll be much harder to filter than

If it's cheap enough, it'll be just like email spam - basically everywhere worth influencing in any way will be flooded. And it'll be much harder to filter than email. One possible solution would be to change basically any community-driven site to be invite-only, and to wield the ban hammer ruthlessly.