For the first time ever, 50% of all American adults are using social networking sites, according to new data from the Pew Internet and American Life Project.

Of active Internet users in particular, 65% are social networking users, a number that continues to climb. To put things in perspective, only 29% of adult American Internet users reported using social networking tools in 2008.

Unsurprisingly, social media usage is even higher among Americans under 30 years old, 61% of whom use sites like Facebook on a daily basis. It's not just younger people who are using the Internet to connect with friends, family and colleagues. The rate at which older people are using the social Web continues to grow as well.

Although the report doesn't break down usage by site, it's safe to assume that the majority of people are partial to Facebook, which has 750 million users worldwide and recently surpassed 1 trillion pageviews in a single month. Facebook CEO Mark Zuckerberg has said he expects the site to reach 1 billion users before long.

Not only do lots of people use social media, they have generally positive attitudes toward it. Reports Pew:

Overall, positive responses far outweighed the negative and neutral words that were associated with social networking sites (more than half of the respondents used positive terms). Users repeatedly described their experiences as "fun," "great," "interesting" and "convenient." Less common were superlatives such as "astounding," "necessity," and "empowering."