The Gilbane Report recently posted the results of their Survey on Enterprise blog, wiki, and RSS Use. While the survey sample is not representative of a larger population of companies (the survey was voluntary and Gilbane readers are probably ahead of the curve), the results are interesting.
Of the 58 respondents (mostly from companies under $25MM in annual revenues but 10 from companies of over $1 Billion in annual revenues.):
Over 35 use Blog or Wiki technology
More of the Blog/Wiki users use them for knowledge management and internal information dissemination, than customer communication.
More than half of the respondents get support for their Blog or Wiki from their internal IT organization.