HubSpot's State of Inbound Marketing report reveals that Facebook, Twitter and LinkedIn are becoming increasingly important channels for bringing in new clients.

Marketers doubting the efficacy of social media campaigns in generating ROI might consider the latest State of Inbound Marketing survey from Hubspot, which indicates that cross-industry brands are acquiring new customers through their social campaigns. Sixty-two percent of businesses say social media marketing has become more important in generating inbound leads in the past six months.

The study asked marketers about their Twitter, Facebook and LinkedIn usage and success. All three platforms have proven to bring in more new clients year-over-year. For instance, 44 percent of marketers say they acquired new customers via Facebook in 2010 compared to 48 percent in 2011. Twitter also showed y-o-y gains, with 42 percent of marketers saying the microblogging site brings in new customers.

LinkedIn showed the most dramatic annual gains. In 2010, 41 percent of businesses said LinkedIn marketing resulted in sales, and this year 57 percent of marketers say the professional-oriented social site brings new customers. This finding supports Brafton's earlier reports that business logins on the site are rising and that LinkedIn is continuously gaining users.

Notably, both B2B and B2C brands are seeing success with social marketing. LinkedIn was especially useful for B2B companies in terms of driving leads, with 61 percent of business-to-business firms gaining new customers through the channel. More than one-third of B2C firms also have success in finding new clients with the site, but Facebook seems best for gaining B2C clients (cited as a valuable source of customers by 67 percent of marketers).

Social media marketing may prove to bring in new customers through other channels as well. As Brafton has reported, Google's Matt Cutts says social marketing is key to SEO, which suggests it can help brands gain traction among search audiences.

Katherine Griwert is Brafton's Marketing Director. She's practiced content marketing, SEO and social marketing for over five years, and her enthusiasm for new media has even deeper roots. Katherine holds a degree in American Studies from Boston College, and her writing is featured in a number of web publications.