To grow, you must delight your users! In addition to building a kickass product that your users love, one area of delight that's often ignored by companies is community management. At Polyvore, we have a dedicated team of community managers whose mission is to delight users. Here's some information about their philosophy and some examples of the work they've done.
This is from a talk I did at TheNextWeb USA conference in NYC on October 7, 2013.