A new study released today shows that consumer use of social networking web sites is not a youth phenomenon. Apparently now at least half of those living in the United States have social media profiles. While nearly eight in ten teens (78 percent) and 18 to 24s (77 percent) have personal profile pages, almost two-thirds of 25 to 34s (65 percent) and half of 35 to 44s (51 percent) also now have personal profile pages. This new national survey from Arbitron Inc.