Four social media agencies are joining forces. Powered, which helps big brands build online communities, has picked up Crayon, Drillteam, and StepChange, in moves that it says will make it the “first full-service social media agency of scale.” Each of the shops has different expertises, although all help big brands establish social media presences; Crayon provides social media marketing consulting services, Drillteam specializes in “earned media,” and StepChange is focused on social networks. Financial details of the deal — which will nearly double the size of Powered workforce, according to AdWeek — were not released. More details in the release. Updated: An SEC filing shows that Powered raised $8.125 million in late December but a spokesman wouldn’t say whether that cash was being used to fund the acquisitions.