According to the newest Pew Internet & American Life Project, the biggest consumer broadband users are young people and households with four or more Internet-connected devices. Here is an introduction from Mary Madden's ALA LITA presentation on "Four or More: The New Demographic". Slideshow (36 slides).
"Trends in social media and cloud computing are often examined through the lens of younger users and broadband users, who have consistently been more actively engaged online when compared with other groups. This presentation highlights new research on teens, young adults and social media use while also identifying a new leading edge group that deserves the same attention: those who own four or more internet-connected devices."