It should come as no surprise that social networking has reached near ubiquity among Internet users here in the U.S. According to recent comScore data, 98 percent of the U.S. online population uses social media, with females spending an average of 7.9 hours per month on social networks, and males spending six.

Also not surprising is Facebook’s dominance. According to the report, titled “It’s a Social World: Top 10 Need-to-Knows About Social Networking and Where It’s Headed,” the 800-million user network reaches 55 percent of the world’s audience, accounting for one in every seven minutes spent online in general and three in every four minutes spent social networking.

Twitter usage grew 59 percent in the past year, now reaching 1 in 10 Internet users worldwide. Tumblr, ranked twelfth, grew 172 percent during the same period. LinkedIn eclipsed Myspace in 2011 as the fourth largest global network. Google+, the fastest network to reach 25 million global unique visitors, now reaches 65 million users, making up 5 percent of the global social networking audience.

Who Is Using Social Networks, and How?

The results of this report are further confirmation of the need for marketers and content creators to pay close and careful attention to social media, as users of all ages flock to this arena.

According to comScore, social networking has reached 94.7 percent of users age 55 and older, representing a 12 percent jump between July 2010 and October 2011. During that same period, the use of email among this group rose merely 1 percent, while email usage among every other age category fell by more than 30 percent, peaking with a 42 percent drop among users age 15-24 (who spend the most amount of time on social networks, at an average of 8.6 hours per month).

Fueling this growth are mobile devices: In the U.S., 64 percent of smartphone users accessed social networking sites at least once in October 2011. While much of this activity is centered on personal use—80 percent used their phones to check posts by people they knew, while 70 percent posted a status—a significant portion of these mobile users are consuming content from brands or public figures: 53.8 percent read posts from organizations, brands and events; 45.3 percent read posts from public figures or celebrities; and 34.4 percent received a coupon, offer or deal.

But while social networking remains increasingly popular among users and marketers (it accounted for 28 percent of display ad impressions in October 2011), it has fallen short of attracting as much revenue, comparatively making up 15 percent of U.S. display ad dollars.