More than half (57%) of adult internet users say they have used a search engine to look up their name and see what information was available about them online, up from 47% who did so in 2006. Young adults, far from being indifferent about their digital footprints, are the most active online reputation managers in several dimensions. For example, more than two-thirds (71%) of social networking users ages 18-29 have changed the privacy settings on their profile to limit what they share with others online.
From the Pew Research Center's Internet & American Life Project.
I'm surprised at that the numbers are lower than I would expect.