This from a just-published report by Eric Mattson and Professor Nora Barnes from the Center for Marketing Research at the University of Massachusetts Dartmouth. They surveyed a representative (+/-3%) segment of the Inc. 500, a list of the U.S’s fastest growing private companies compiled by Inc. Magazine. 26% said that social media is (are?) “very important” to their business marketing strategy. Here are the rates of usage for various social media:

33% message or bulletin boards
27% social networking
24% online video
19% blogging
17% wikis
11% podcasting (which is the only figure that actually dovetails with use. A recent Pew American Life report showed 12% of U.S. Internet users have downloaded a podcast).

You can read the executive summary of the report here