Agencies play a critical role in your social media marketing's success. But the agency space is crowded and few do it all well, forcing interactive marketers to patch together a portfolio of partners. Compounding the problem, many established agencies fail to provide the needed expertise. But their shortcomings created the opportunity for a new type of agency to step in: the social media boutique agency. When should you hire one of these new firms? When your incumbent agencies fail to meet your social media needs; when you have the ability and tolerance to add another player to your roster; and when you've charted a clear long-term role for the newcomer.