Jeremiah Owyang has a good rundown of current discussions among PR and media luminaries about whether social media are "adopted" or not.
My initial response: "So, what else is new?"
Adoption rates for social media vary widely by industry, company, social demographic, and whatever other population descriptor you want to use. I figure the "big picture" for the general population looks something like this (note that these data are totally made up):
Since I frequently deal with more specialized populations (for example, I'm currently developing a social media seminar for a large professional membership association) I figure that more specialized professional populations look something like this:
While the data in the above figures totally made up, they do express my belief that such adoption rates may differ substantially among groups. To develop an effective strategy to employ such media, you need to understand both the current situation of your target group as well as your group's level of engagement with other groups, media, and information sources.
Not that this should be a surprise to anyone. Once you move beyond evangelism and hype into the nuts and bolts about providing concrete benefits, it helps to have a grounding in reality. Figuring out what figures like the above really look like for a given population group might not be such a bad place to start.