For several years now, conversation on social media has been locked in mortal battle with campaigning. Spontaneous user-driven conversations are increasingly crowded out by content that companies and organizations have disseminated across the social web by paying for high-quality production, advertising, and promotions.But for a while, one online service seemed to hold conversation and campaigning in balance: Topsy, acquired by Apple in 2013 and shuttered abruptly by the Cupertino behemoth last week.Hasty obituaries for Topsy described it as an