Notice to companies getting started in social media: You’re not an early adopter.

The most advanced firms are among Inc. magazine’s 500 fastest-growing companies, according to a survey by the Center of Marketing Research at the University of Massachusetts Dartmouth.

They’re ahead of the Fortune 500, which presumably means that they’re ahead of everyone.

Of those surveyed, 80% use social media. That’s up from 49% in 2008. And 14% are planning to use it.

Over two thirds monitor their brands in the social networks, and a third use the networks to communicate with vendors and partners. In addition, almost half use this new channel to recruit and evaluate employment candidates.

Meanwhile, 75% are “very familiar” with social media, compared with 57% in 2008. And 87% say that the social networks have been successful in generating hits, comments, leads or sales.

At the same time, the growth of wikis, podcasts and message boards has “leveled off or declined,” according to Nora Ganim Barnes, Ph.D. and Eric Mattson, the authors of the report.

But there are a couple of contradictions:

1. While growth in wiki and message board usage has flattened, these tools apparently produce results. Of the respondents using wikis, 92% say they are successful, and 91% say the same about message boards. The other channels also do pretty well.

2. Familiarity and adoption are not the same thing. “While familiarity is related to adoption, even the least familiar tool has 37% adoption (podcasting),” the authors write.

As for the future, you can expect social media to get even more dominant.

Of those polled, 43% said that social media are a very important part of their business/marketing strategies, and 36% consider them somewhat important. That’s flat with last year. But the percentage that sees them as “very unimportant” is in the low single digits.

The conclusion? “This research proves once again that social media has penetrated parts of the business world at a tremendous speed,” the authors write. “It also indicates that corporate familiarity within the inc. 500 has continued to grow in the last 12 months.”

Of the firms listed in Inc. 500, 148 participated in the telephone survey. For the full survey, click here.