The nation's fastest-growing private companies are making use of social media -- including blogs, social networking and podcasts -- at a rate more than twice that of Fortune 500 companies, according to a new study.

The University of Massachusetts-Dartmouth's Center for Marketing Research surveyed companies from the 2006 Inc. 500 list, to gauge the level of familiarity and usage of six forms of social media -- blogging, podcasting, online video, social networking and wikis. Out of 121 respondents, generally managers and other senior-level executives, 42 percent claimed to be "very familiar" with social networking, followed by 38 percent with message boards and 31 percent with blogging.

Across the board, respondents were familiar with all types of social media, including 16 percent being very familiar with wikis, which are typically a lesser-known type of social media on average.

Companies were also asked about their actual usage of the various types of social media, and message boards had the highest adoption rate at 33 percent, followed closely by social networking  at 27 percent. Blogging had a lower percentage of usage among respondents at 19 percent, and podcasting was the type of social media with the lowest adoption rate at 11 percent.

"These responses are surprising and will likely shock even the most fervent believer in social media," Nora Ganim Barnes, director of the Center for Marketing Research and a leader of the study, said in a statement. "They indicate that corporate familiarity and usage of social media is racing far ahead of what many have predicted."

These results contrast with previous research that found only 8 percent of Fortune 500 companies have a public blog. The purpose of the study, which was not conducted at the request or on behalf of Inc. magazine or, was to see if there was a difference in the knowledge and usage of social media in companies selected by growth rather than revenue. The respondents represented a wide range of the Inc. 500 and were diverse in terms of industry, size, and location. Four respondents were in the top 10 of the list, seven were in the top 25 and 22 held one of the top 100 spots.

Additionally, a majority of the Inc. 500 companies acknowledged the critical role that social media plays for their future success, with two out of three respondents indicating that it is "very important" or "somewhat important" to their business and marketing strategies. A breakdown of the results shows that 26 percent deemed it "very important" while 40 percent thought it was "somewhat important."

"For those of us who have been following fast-growth companies for years, it's no surprise that they would be at the forefront of using innovative technologies to enhance their visibility, marketing, and interaction with other companies," said Edward Sussman, senior vice president of Mansueto Ventures, the publisher of Inc. and

Inc. will expand the list 10-fold this year, to become the first-ever Inc. 5,000, ranking the nation's 5,000 fastest-growing private companies.